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locale.module

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    system.api.php 120.88 KiB
    <?php
    // $Id$
    
    /**
     * @file
     * Hooks provided by Drupal core and the System module.
     */
    
    /**
     * @addtogroup hooks
     * @{
     */
    
    /**
     * Defines one or more hooks that are exposed by a module.
     *
     * Normally hooks do not need to be explicitly defined. However, by declaring a
     * hook explicitly, a module may define a "group" for it. Modules that implement
     * a hook may then place their implementation in either $module.module or in
     * $module.$group.inc. If the hook is located in $module.$group.inc, then that
     * file will be automatically loaded when needed.
     * In general, hooks that are rarely invoked and/or are very large should be
     * placed in a separate include file, while hooks that are very short or very
     * frequently called should be left in the main module file so that they are
     * always available.
     *
     * @return
     *   An associative array whose keys are hook names and whose values are an
     *   associative array containing:
     *   - group: A string defining the group to which the hook belongs. The module
     *     system will determine whether a file with the name $module.$group.inc
     *     exists, and automatically load it when required.
     *
     * See system_hook_info() for all hook groups defined by Drupal core.
     */
    function hook_hook_info() {
      $hooks['token_info'] = array(
        'group' => 'tokens',
      );
      $hooks['tokens'] = array(
        'group' => 'tokens',
      );
      return $hooks;
    }
    
    /**
     * Inform the base system and the Field API about one or more entity types.
     *
     * Inform the system about one or more entity types (i.e., object types that
     * can be loaded via entity_load() and, optionally, to which fields can be
     * attached).
     *
     * @see entity_load()
     * @see hook_entity_info_alter()
     *
     * @return
     *   An array whose keys are entity type names and whose values identify
     *   properties of those types that the system needs to know about:
     *   - label: The human-readable name of the type.
     *   - controller class: The name of the class that is used to load the objects.
     *     The class has to implement the DrupalEntityControllerInterface interface.
     *     Leave blank to use the DrupalDefaultEntityController implementation.
     *   - base table: (used by DrupalDefaultEntityController) The name of the
     *     entity type's base table.
     *   - static cache: (used by DrupalDefaultEntityController) FALSE to disable
     *     static caching of entities during a page request. Defaults to TRUE.
     *   - load hook: The name of the hook which should be invoked by
     *     DrupalDefaultEntityController:attachLoad(), for example 'node_load'.
     *   - uri callback: A function taking an entity as argument and returning the
     *     uri elements of the entity, e.g. 'path' and 'options'. The actual entity
     *     uri can be constructed by passing these elements to url().
     *   - fieldable: Set to TRUE if you want your entity type to be fieldable.
     *   - object keys: An array describing how the Field API can extract the
     *     information it needs from the objects of the type. Elements:
     *     - id: The name of the property that contains the primary id of the
     *       object. Every object passed to the Field API must have this property
     *       and its value must be numeric.
     *     - revision: The name of the property that contains the revision id of
     *       the object. The Field API assumes that all revision ids are unique
     *       across all objects of a type.
     *       This element can be omitted if the objects of this type are not
     *       versionable.
     *     - bundle: The name of the property that contains the bundle name for the
     *       object. The bundle name defines which set of fields are attached to
     *       the object (e.g. what nodes call "content type").
     *       This element can be omitted if this type has no bundles (all objects
     *       have the same fields).
     *   - bundle keys: An array describing how the Field API can extract the
     *     information it needs from the bundle objects for this type (e.g
     *     $vocabulary objects for terms; not applicable for nodes).
     *     This element can be omitted if this type's bundles do not exist as
     *     standalone objects. Elements:
     *     - bundle: The name of the property that contains the name of the bundle
     *       object.
     *   - cacheable: A boolean indicating whether Field API should cache
     *     loaded fields for each object, reducing the cost of
     *     field_attach_load().
     *   - bundles: An array describing all bundles for this object type.
     *     Keys are bundles machine names, as found in the objects' 'bundle'
     *     property (defined in the 'object keys' entry above). Elements:
     *     - label: The human-readable name of the bundle.
     *     - admin: An array of information that allows Field UI pages to attach
     *       themselves to the existing administration pages for the bundle.
     *       Elements:
     *       - path: the path of the bundle's main administration page, as defined
     *         in hook_menu(). If the path includes a placeholder for the bundle,
     *         the 'bundle argument', 'bundle helper' and 'real path' keys below
     *         are required.
     *       - bundle argument: The position of the placeholder in 'path', if any.
     *       - real path: The actual path (no placeholder) of the bundle's main
     *         administration page. This will be used to generate links.
     *       - access callback: As in hook_menu(). 'user_access' will be assumed if
     *         no value is provided.
     *       - access arguments: As in hook_menu().
     *   - view modes: An array describing the view modes for the entity type. View
     *     modes let entities be displayed differently depending on the context.
     *     For instance, a node can be displayed differently on its own page
     *     ('full' mode), on the home page or taxonomy listings ('teaser' mode), or
     *     in an RSS feed ('rss' mode). Modules taking part in the display of the
     *     entity (notably the Field API) can adjust their behavior depending on
     *     the requested view mode. Keys of the array are view mode names. Each
     *     view mode is described by an array with the following key/value pairs:
     *     - label: The human-readable name of the view mode
     */
    function hook_entity_info() {
      $return = array(
        'node' => array(
          'label' => t('Node'),
          'controller class' => 'NodeController',
          'base table' => 'node',
          'revision table' => 'node_revision',
          'path callback' => 'node_path',
          'fieldable' => TRUE,
          'object keys' => array(
            'id' => 'nid',
            'revision' => 'vid',
            'bundle' => 'type',
          ),
          'bundle keys' => array(
            'bundle' => 'type',
          ),
          // Node.module handles its own caching.
          // 'cacheable' => FALSE,
          'bundles' => array(),
          'view modes' => array(
            'full' => array(
              'label' => t('Full node'),
            ),
            'teaser' => array(
              'label' => t('Teaser'),
            ),
            'rss' => array(
              'label' => t('RSS'),
            ),
          ),
        ),
      );
    
      // Search integration is provided by node.module, so search-related
      // view modes for nodes are defined here and not in search.module.
      if (module_exists('search')) {
        $return['node']['view modes'] += array(
          'search_index' => array(
            'label' => t('Search index'),
          ),
          'search_result' => array(
            'label' => t('Search result'),
          ),
        );
      }
    
      // Bundles must provide a human readable name so we can create help and error
      // messages, and the path to attach Field admin pages to.
      foreach (node_type_get_names() as $type => $name) {
        $return['node']['bundles'][$type] = array(
          'label' => $name,
          'admin' => array(
            'path' => 'admin/structure/types/manage/%node_type',
            'real path' => 'admin/structure/types/manage/' . str_replace('_', '-', $type),
            'bundle argument' => 4,
            'access arguments' => array('administer content types'),
          ),
        );
      }
    
      return $return;
    }
    
    /**
     * Alter the entity info.
     *
     * Modules may implement this hook to alter the information that defines an
     * entity. All properties that are available in hook_entity_info() can be
     * altered here.
     *
     * @see hook_entity_info()
     *
     * @param $entity_info
     *   The entity info array, keyed by entity name.
     */
    function hook_entity_info_alter(&$entity_info) {
      // Set the controller class for nodes to an alternate implementation of the
      // DrupalEntityController interface.
      $entity_info['node']['controller class'] = 'MyCustomNodeController';
    }
    
    /**
     * Act on entities when loaded.
     *
     * This is a generic load hook called for all entity types loaded via the
     * entity API.
     *
     * @param $entities
     *   The entities keyed by entity ID.
     * @param $type
     *   The type of entities being loaded (i.e. node, user, comment).
     */
    function hook_entity_load($entities, $type) {
      foreach ($entities as $entity) {
        $entity->foo = mymodule_add_something($entity, $type);
      }
    }
    
    /**
     * Act on entities when inserted.
     *
     * Generic insert hook called for all entity types via entity_invoke().
     *
     * @param $entity
     *   The entity object.
     * @param $type
     *   The type of entity being inserted (i.e. node, user, comment).
     */
    function hook_entity_insert($entity, $type) {
    }
    
    /**
     * Act on entities when updated.
     *
     * Generic update hook called for all entity types via entity_invoke().
     *
     * @param $entity
     *   The entity object.
     * @param $type
     *   The type of entity being updated (i.e. node, user, comment).
     */
    function hook_entity_update($entity, $type) {
    }
    
    /**
     * Define administrative paths.
     *
     * Modules may specify whether or not the paths they define in hook_menu() are
     * to be considered administrative. Other modules may use this information to
     * display those pages differently (e.g. in a modal overlay, or in a different
     * theme).
     *
     * To change the administrative status of menu items defined in another module's
     * hook_menu(), modules should implement hook_admin_paths_alter().
     *
     * @return
     *   An associative array. For each item, the key is the path in question, in
     *   a format acceptable to drupal_match_path(). The value for each item should
     *   be TRUE (for paths considered administrative) or FALSE (for non-
     *   administrative paths).
     *
     * @see hook_menu()
     * @see drupal_match_path()
     * @see hook_admin_paths_alter()
     */
    function hook_admin_paths() {
      $paths = array(
        'mymodule/*/add' => TRUE,
        'mymodule/*/edit' => TRUE,
      );
      return $paths;
    }
    
    /**
     * Redefine administrative paths defined by other modules.
     *
     * @param $paths
     *   An associative array of administrative paths, as defined by implementations
     *   of hook_admin_paths().
     *
     * @see hook_admin_paths()
     */
    function hook_admin_paths_alter(&$paths) {
      // Treat all user pages as administrative.
      $paths['user'] = TRUE;
      $paths['user/*'] = TRUE;
      // Treat the forum topic node form as a non-administrative page.
      $paths['node/add/forum'] = FALSE;
    }
    
    /**
     * Act on entities as they are being prepared for view.
     *
     * Allows you to operate on multiple entities as they are being prepared for
     * view. Only use this if attaching the data during the entity_load() phase
     * is not appropriate, for example when attaching other 'entity' style objects.
     *
     * @param $entities
     *   The entities keyed by entity ID.
     * @param $type
     *   The type of entities being loaded (i.e. node, user, comment).
     */
    function hook_entity_prepare_view($entities, $type) {
      // Load a specific node into the user object for later theming.
      if ($type == 'user') {
        $nodes = mymodule_get_user_nodes(array_keys($entities));
        foreach ($entities as $uid => $entity) {
          $entity->user_node = $nodes[$uid];
        }
      }
    }
    
    /**
     * Perform periodic actions.
     *
     * This hook will only be called if cron.php is run (e.g. by crontab).
     *
     * Modules that require to schedule some commands to be executed at regular
     * intervals can implement hook_cron(). The engine will then call the hook
     * at the appropriate intervals defined by the administrator. This interface
     * is particularly handy to implement timers or to automate certain tasks.
     * Database maintenance, recalculation of settings or parameters are good
     * candidates for cron tasks.
     *
     * Short-running or not resource intensive tasks can be executed directly.
     *
     * Long-running tasks should use the queue API. To do this, one or more queues
     * need to be defined via hook_cron_queue_info(). Items that need to be
     * processed are appended to the defined queue, instead of processing them
     * directly in hook_cron().
     * Examples of jobs that are good candidates for
     * hook_cron_queue_info() include automated mailing, retrieving remote data, and
     * intensive file tasks.
     *
     * @return
     *   None.
     *
     * @see hook_cron_queue_info()
     */
    function hook_cron() {
      // Short-running operation example, not using a queue:
      // Delete all expired records since the last cron run.
      $expires = variable_get('mymodule_cron_last_run', REQUEST_TIME);
      db_delete('mymodule_table')
        ->condition('expires', $expires, '>=')
        ->execute();
      variable_set('mymodule_cron_last_run', REQUEST_TIME);
    
      // Long-running operation example, leveraging a queue:
      // Fetch feeds from other sites.
      $result = db_query('SELECT * FROM {aggregator_feed} WHERE checked + refresh < :time AND refresh != :never', array(
        ':time' => REQUEST_TIME,
        ':never' => AGGREGATOR_CLEAR_NEVER,
      ));
      $queue = DrupalQueue::get('aggregator_feeds');
      foreach ($result as $feed) {
        $queue->createItem($feed);
      }
    }
    
    /**
     * Declare queues holding items that need to be run periodically.
     *
     * While there can be only one hook_cron() process running at the same time,
     * there can be any number of processes defined here running. Because of
     * this, long running tasks are much better suited for this API. Items queued
     * in hook_cron() might be processed in the same cron run if there are not many
     * items in the queue, otherwise it might take several requests, which can be
     * run in parallel.
     *
     * @return
     *   An associative array where the key is the queue name and the value is
     *   again an associative array. Possible keys are:
     *   - 'worker callback': The name of the function to call. It will be called
     *     with one argument, the item created via DrupalQueue::createItem() in
     *     hook_cron().
     *   - 'time': (optional) How much time Drupal should spend on calling this
     *     worker in seconds. Defaults to 15.
     *
     * @see hook_cron()
     */
    function hook_cron_queue_info() {
      $queues['aggregator_feeds'] = array(
        'worker callback' => 'aggregator_refresh',
        'time' => 15,
      );
      return $queues;
    }
    
    /**
     * Allows modules to declare their own Forms API element types and specify their
     * default values.
     *
     * This hook allows modules to declare their own form element types and to
     * specify their default values. The values returned by this hook will be
     * merged with the elements returned by hook_form() implementations and so
     * can return defaults for any Form APIs keys in addition to those explicitly
     * mentioned below.
     *
     * Each of the form element types defined by this hook is assumed to have
     * a matching theme function, e.g. theme_elementtype(), which should be
     * registered with hook_theme() as normal.
     *
     * Form more information about custom element types see the explanation at
     * http://drupal.org/node/169815.
     *
     * @return
     *  An associative array describing the element types being defined. The array
     *  contains a sub-array for each element type, with the machine-readable type
     *  name as the key. Each sub-array has a number of possible attributes:
     *  - "#input": boolean indicating whether or not this element carries a value
     *    (even if it's hidden).
     *  - "#process": array of callback functions taking $element, $form_state,
     *    and $complete_form.
     *  - "#after_build": array of callback functions taking $element and $form_state.
     *  - "#validate": array of callback functions taking $form and $form_state.
     *  - "#element_validate": array of callback functions taking $element and
     *    $form_state.
     *  - "#pre_render": array of callback functions taking $element and $form_state.
     *  - "#post_render": array of callback functions taking $element and $form_state.
     *  - "#submit": array of callback functions taking $form and $form_state.
     *  - "#title_display": optional string indicating if and how #title should be
     *    displayed, see theme_form_element() and theme_form_element_label().
     *
     * @see hook_element_info_alter()
     * @see system_element_info()
     */
    function hook_element_info() {
      $types['filter_format'] = array(
        '#input' => TRUE,
      );
      return $types;
    }
    
    /**
     * Alter the element type information returned from modules.
     *
     * A module may implement this hook in order to alter the element type defaults
     * defined by a module.
     *
     * @param &$type
     *   All element type defaults as collected by hook_element_info().
     *
     * @see hook_element_info()
     */
    function hook_element_info_alter(&$type) {
      // Decrease the default size of textfields.
      if (isset($type['textfield']['#size'])) {
        $type['textfield']['#size'] = 40;
      }
    }
    
    /**
     * Perform cleanup tasks.
     *
     * This hook is run at the end of each page request. It is often used for
     * page logging and specialized cleanup. This hook MUST NOT print anything.
     *
     * Only use this hook if your code must run even for cached page views.
     * If you have code which must run once on all non cached pages, use
     * hook_init instead. Thats the usual case. If you implement this hook
     * and see an error like 'Call to undefined function', it is likely that
     * you are depending on the presence of a module which has not been loaded yet.
     * It is not loaded because Drupal is still in bootstrap mode.
     *
     * @param $destination
     *   If this hook is invoked as part of a drupal_goto() call, then this argument
     *   will be a fully-qualified URL that is the destination of the redirect.
     */
    function hook_exit($destination = NULL) {
      db_update('counter')
        ->expression('hits', 'hits + 1')
        ->condition('type', 1)
        ->execute();
    }
    
    /**
     * Perform necessary alterations to the JavaScript before it is presented on
     * the page.
     *
     * @param $javascript
     *   An array of all JavaScript being presented on the page.
     * @see drupal_add_js()
     * @see drupal_get_js()
     * @see drupal_js_defaults()
     */
    function hook_js_alter(&$javascript) {
      // Swap out jQuery to use an updated version of the library.
      $javascript['misc/jquery.js']['data'] = drupal_get_path('module', 'jquery_update') . '/jquery.js';
    }
    
    /**
     * Registers JavaScript/CSS libraries associated with a module.
     *
     * Modules implementing this return an array of arrays. The key to each
     * sub-array is the machine readable name of the library. Each library may
     * contain the following items:
     *
     * - 'title': The human readable name of the library.
     * - 'website': The URL of the library's web site.
     * - 'version': A string specifying the version of the library; intentionally
     *   not a float because a version like "1.2.3" is not a valid float. Use PHP's
     *   version_compare() to compare different versions.
     * - 'js': An array of JavaScript elements; each element's key is used as $data
     *   argument, each element's value is used as $options array for
     *   drupal_add_js(). To add library-specific (not module-specific) JavaScript
     *   settings, the key may be skipped, the value must specify
     *   'type' => 'setting', and the actual settings must be contained in a 'data'
     *   element of the value.
     * - 'css': Like 'js', an array of CSS elements passed to drupal_add_css().
     * - 'dependencies': An array of libraries that are required for a library. Each
     *   element is an array containing the module and name of the registered
     *   library. Note that all dependencies for each dependent library will be
     *   added when this library is added.
     *
     * Registered information for a library should contain re-usable data only.
     * Module- or implementation-specific data and integration logic should be added
     * separately.
     *
     * @return
     *   An array defining libraries associated with a module.
     *
     * @see system_library()
     * @see drupal_add_library()
     * @see drupal_get_library()
     */
    function hook_library() {
      // Library One.
      $libraries['library-1'] = array(
        'title' => 'Library One',
        'website' => 'http://example.com/library-1',
        'version' => '1.2',
        'js' => array(
          drupal_get_path('module', 'my_module') . '/library-1.js' => array(),
        ),
        'css' => array(
          drupal_get_path('module', 'my_module') . '/library-2.css' => array(
            'type' => 'file',
            'media' => 'screen',
          ),
        ),
      );
      // Library Two.
      $libraries['library-2'] = array(
        'title' => 'Library Two',
        'website' => 'http://example.com/library-2',
        'version' => '3.1-beta1',
        'js' => array(
          // JavaScript settings may use the 'data' key.
          array(
            'type' => 'setting',
            'data' => array('library2' => TRUE),
          ),
        ),
        'dependencies' => array(
          // Require jQuery UI core by System module.
          array('system' => 'ui'),
          // Require our other library.
          array('my_module', 'library-1'),
          // Require another library.
          array('other_module', 'library-3'),
        ),
      );
      return $libraries;
    }
    
    /**
     * Alters the JavaScript/CSS library registry.
     *
     * Allows certain, contributed modules to update libraries to newer versions
     * while ensuring backwards compatibility. In general, such manipulations should
     * only be done by designated modules, since most modules that integrate with a
     * certain library also depend on the API of a certain library version.
     *
     * @param $libraries
     *   The JavaScript/CSS libraries provided by $module. Keyed by internal library
     *   name and passed by reference.
     * @param $module
     *   The name of the module that registered the libraries.
     *
     * @see hook_library()
     */
    function hook_library_alter(&$libraries, $module) {
      // Update Farbtastic to version 2.0.
      if ($module == 'system' && isset($libraries['farbtastic'])) {
        // Verify existing version is older than the one we are updating to.
        if (version_compare($libraries['farbtastic']['version'], '2.0', '<')) {
          // Update the existing Farbtastic to version 2.0.
          $libraries['farbtastic']['version'] = '2.0';
          $libraries['farbtastic']['js'] = array(
            drupal_get_path('module', 'farbtastic_update') . '/farbtastic-2.0.js' => array(),
          );
        }
      }
    }
    
    /**
     * Alter CSS files before they are output on the page.
     *
     * @param $css
     *   An array of all CSS items (files and inline CSS) being requested on the page.
     * @see drupal_add_css()
     * @see drupal_get_css()
     */
    function hook_css_alter(&$css) {
      // Remove defaults.css file.
      unset($css[drupal_get_path('module', 'system') . '/defaults.css']);
    }
    
    /**
     * Alter the commands that are sent to the user through the AJAX framework.
     *
     * @param $commands
     *   An array of all commands that will be sent to the user.
     * @see ajax_render()
     */
    function hook_ajax_render_alter($commands) {
      // Inject any new status messages into the content area.
      $commands[] = ajax_command_prepend('#block-system-main .content', theme('status_messages'));
    }
    
    /**
     * Add elements to a page before it is rendered.
     *
     * Use this hook when you want to add elements at the page level. For your
     * additions to be printed, they have to be placed below a top level array key
     * of the $page array that has the name of a region of the active theme.
     *
     * By default, valid region keys are 'page_top', 'header', 'sidebar_first',
     * 'content', 'sidebar_second' and 'page_bottom'. To get a list of all regions
     * of the active theme, use system_region_list($theme). Note that $theme is a
     * global variable.
     *
     * If you want to alter the elements added by other modules or if your module
     * depends on the elements of other modules, use hook_page_alter() instead which
     * runs after this hook.
     *
     * @param $page
     *   Nested array of renderable elements that make up the page.
     *
     * @see hook_page_alter()
     * @see drupal_render_page()
     */
    function hook_page_build(&$page) {
      if (menu_get_object('node', 1)) {
        // We are on a node detail page. Append a standard disclaimer to the
        // content region.
        $page['content']['disclaimer'] = array(
          '#markup' => t('Acme, Inc. is not responsible for the contents of this sample code.'),
          '#weight' => 25,
        );
      }
    }
    
    /**
     * Perform alterations before a page is rendered.
     *
     * Use this hook when you want to remove or alter elements at the page
     * level, or add elements at the page level that depend on an other module's
     * elements (this hook runs after hook_page_build().
     *
     * If you are making changes to entities such as forms, menus, or user
     * profiles, use those objects' native alter hooks instead (hook_form_alter(),
     * for example).
     *
     * The $page array contains top level elements for each block region:
     * @code
     *   $page['page_top']
     *   $page['header']
     *   $page['sidebar_first']
     *   $page['content']
     *   $page['sidebar_second']
     *   $page['page_bottom']
     * @endcode
     *
     * The 'content' element contains the main content of the current page, and its
     * structure will vary depending on what module is responsible for building the
     * page. Some legacy modules may not return structured content at all: their
     * pre-rendered markup will be located in $page['content']['main']['#markup'].
     *
     * Pages built by Drupal's core Node and Blog modules use a standard structure:
     *
     * @code
     *   // Node body.
     *   $page['content']['nodes'][$nid]['body']
     *   // Array of links attached to the node (add comments, read more).
     *   $page['content']['nodes'][$nid]['links']
     *   // The node object itself.
     *   $page['content']['nodes'][$nid]['#node']
     *   // The results pager.
     *   $page['content']['pager']
     * @endcode
     *
     * Blocks may be referenced by their module/delta pair within a region:
     * @code
     *   // The login block in the first sidebar region.
     *   $page['sidebar_first']['user_login']['#block'];
     * @endcode
     *
     * @param $page
     *   Nested array of renderable elements that make up the page.
     *
     * @see hook_page_build()
     * @see drupal_render_page()
     */
    function hook_page_alter(&$page) {
      // Add help text to the user login block.
      $page['sidebar_first']['user_login']['help'] = array(
        '#weight' => -10,
        '#markup' => t('To post comments or add new content, you first have to log in.'),
      );
    }
    
    /**
     * Perform alterations before a form is rendered.
     *
     * One popular use of this hook is to add form elements to the node form. When
     * altering a node form, the node object retrieved at from $form['#node'].
     *
     * Note that instead of hook_form_alter(), which is called for all forms, you
     * can also use hook_form_FORM_ID_alter() to alter a specific form.
     *
     * @param $form
     *   Nested array of form elements that comprise the form.
     * @param $form_state
     *   A keyed array containing the current state of the form.
     * @param $form_id
     *   String representing the name of the form itself. Typically this is the
     *   name of the function that generated the form.
     */
    function hook_form_alter(&$form, &$form_state, $form_id) {
      if (isset($form['type']) && $form['type']['#value'] . '_node_settings' == $form_id) {
        $form['workflow']['upload_' . $form['type']['#value']] = array(
          '#type' => 'radios',
          '#title' => t('Attachments'),
          '#default_value' => variable_get('upload_' . $form['type']['#value'], 1),
          '#options' => array(t('Disabled'), t('Enabled')),
        );
      }
    }
    
    /**
     * Provide a form-specific alteration instead of the global hook_form_alter().
     *
     * Modules can implement hook_form_FORM_ID_alter() to modify a specific form,
     * rather than implementing hook_form_alter() and checking the form ID, or
     * using long switch statements to alter multiple forms.
     *
     * Note that this hook fires before hook_form_alter(). Therefore all
     * implementations of hook_form_FORM_ID_alter() will run before all implementations
     * of hook_form_alter(), regardless of the module order.
     *
     * @param $form
     *   Nested array of form elements that comprise the form.
     * @param $form_state
     *   A keyed array containing the current state of the form.
     *
     * @see drupal_prepare_form().
     */
    function hook_form_FORM_ID_alter(&$form, &$form_state) {
      // Modification for the form with the given form ID goes here. For example, if
      // FORM_ID is "user_register_form" this code would run only on the user
      // registration form.
    
      // Add a checkbox to registration form about agreeing to terms of use.
      $form['terms_of_use'] = array(
        '#type' => 'checkbox',
        '#title' => t("I agree with the website's terms and conditions."),
        '#required' => TRUE,
      );
    }
    
    /**
     * Allow themes to alter the theme-specific settings form.
     *
     * With this hook, themes can alter the theme-specific settings form in any way
     * allowable by Drupal's Forms API, such as adding form elements, changing
     * default values and removing form elements. See the Forms API documentation on
     * api.drupal.org for detailed information.
     *
     * Note that the base theme's form alterations will be run before any sub-theme
     * alterations.
     *
     * @param $form
     *   Nested array of form elements that comprise the form.
     * @param $form_state
     *   A keyed array containing the current state of the form.
     */
    function hook_form_system_theme_settings_alter(&$form, &$form_state) {
      // Add a checkbox to toggle the breadcrumb trail.
      $form['toggle_breadcrumb'] = array(
        '#type' => 'checkbox',
        '#title' => t('Display the breadcrumb'),
        '#default_value' => theme_get_setting('toggle_breadcrumb'),
        '#description'   => t('Show a trail of links from the homepage to the current page.'),
      );
    }
    
    /**
     * Map form_ids to builder functions.
     *
     * This hook allows modules to build multiple forms from a single form "factory"
     * function but each form will have a different form id for submission,
     * validation, theming or alteration by other modules.
     *
     * The 'callback arguments' will be passed as parameters to the function defined
     * in 'callback'. In case the code that calls drupal_get_form() also passes
     * parameters, then the 'callback' function will receive the
     * 'callback arguments' specified in hook_forms() before those that have been
     * passed to drupal_get_form().
     *
     * See node_forms() for an actual example of how multiple forms share a common
     * building function.
     *
     * @param $form_id
     *   The unique string identifying the desired form.
     * @param $args
     *   An array containing the original arguments provided to drupal_get_form().
     *   These are always passed to the form builder and do not have to be specified
     *   manually in 'callback arguments'.
     *
     * @return
     *   An associative array whose keys define form_ids and whose values are an
     *   associative array defining the following keys:
     *   - callback: The name of the form builder function to invoke.
     *   - callback arguments: (optional) Additional arguments to pass to the
     *     function defined in 'callback', which are prepended to $args.
     *   - wrapper_callback: (optional) The name of a form builder function to
     *     invoke before the form builder defined in 'callback' is invoked. This
     *     wrapper callback may prepopulate the $form array with form elements,
     *     which will then be already contained in the $form that is passed on to
     *     the form builder defined in 'callback'. For example, a wrapper callback
     *     could setup wizard-alike form buttons that are the same for a variety of
     *     forms that belong to the wizard, which all share the same wrapper
     *     callback.
     */
    function hook_forms($form_id, $args) {
      // Simply reroute the (non-existing) $form_id 'mymodule_first_form' to
      // 'mymodule_main_form'.
      $forms['mymodule_first_form'] = array(
        'callback' => 'mymodule_main_form',
      );
    
      // Reroute the $form_id and prepend an additional argument that gets passed to
      // the 'mymodule_main_form' form builder function.
      $forms['mymodule_second_form'] = array(
        'callback' => 'mymodule_main_form',
        'callback arguments' => array('some parameter'),
      );
    
      // Reroute the $form_id, but invoke the form builder function
      // 'mymodule_main_form_wrapper' first, so we can prepopulate the $form array
      // that is passed to the actual form builder 'mymodule_main_form'.
      $forms['mymodule_wrapped_form'] = array(
        'callback' => 'mymodule_main_form',
        'wrapper_callback' => 'mymodule_main_form_wrapper',
      );
    
      return $forms;
    }
    
    /**
     * Perform setup tasks. See also, hook_init.
     *
     * This hook is run at the beginning of the page request. It is typically
     * used to set up global parameters which are needed later in the request.
     *
     * Only use this hook if your code must run even for cached page views.This hook
     * is called before modules or most include files are loaded into memory.
     * It happens while Drupal is still in bootstrap mode.
     */
    function hook_boot() {
      // we need user_access() in the shutdown function. make sure it gets loaded
      drupal_load('module', 'user');
      drupal_register_shutdown_function('devel_shutdown');
    }
    
    /**
     * Perform setup tasks. See also, hook_boot.
     *
     * This hook is run at the beginning of the page request. It is typically
     * used to set up global parameters which are needed later in the request.
     * when this hook is called, all modules are already loaded in memory.
     *
     * For example, this hook is a typical place for modules to add CSS or JS
     * that should be present on every page. This hook is not run on cached
     * pages - though CSS or JS added this way will be present on a cached page.
     */
    function hook_init() {
      drupal_add_css(drupal_get_path('module', 'book') . '/book.css');
    }
    
    /**
     * Define image toolkits provided by this module.
     *
     * The file which includes each toolkit's functions must be declared as part of
     * the files array in the module .info file so that the registry will find and
     * parse it.
     *
     * The toolkit's functions must be named image_toolkitname_operation().
     * where the operation may be:
     *   - 'load': Required. See image_gd_load() for usage.
     *   - 'save': Required. See image_gd_save() for usage.
     *   - 'settings': Optional. See image_gd_settings() for usage.
     *   - 'resize': Optional. See image_gd_resize() for usage.
     *   - 'rotate': Optional. See image_gd_rotate() for usage.
     *   - 'crop': Optional. See image_gd_crop() for usage.
     *   - 'desaturate': Optional. See image_gd_desaturate() for usage.
     *
     * @return
     *   An array with the toolkit name as keys and sub-arrays with these keys:
     *     - 'title': A string with the toolkit's title.
     *     - 'available': A Boolean value to indicate that the toolkit is operating
     *       properly, e.g. all required libraries exist.
     *
     * @see system_image_toolkits()
     */
    function hook_image_toolkits() {
      return array(
        'working' => array(
          'title' => t('A toolkit that works.'),
          'available' => TRUE,
        ),
        'broken' => array(
          'title' => t('A toolkit that is "broken" and will not be listed.'),
          'available' => FALSE,
        ),
      );
    }
    
    /**
     * Alter an email message created with the drupal_mail() function.
     *
     * hook_mail_alter() allows modification of email messages created and sent
     * with drupal_mail(). Usage examples include adding and/or changing message
     * text, message fields, and message headers.
     *
     * Email messages sent using functions other than drupal_mail() will not
     * invoke hook_mail_alter(). For example, a contributed module directly
     * calling the drupal_mail_system()->mail() or PHP mail() function
     * will not invoke this hook. All core modules use drupal_mail() for
     * messaging, it is best practice but not mandatory in contributed modules.
     *
     * @param $message
     *   An array containing the message data. Keys in this array include:
     *  - 'id':
     *     The drupal_mail() id of the message. Look at module source code or
     *     drupal_mail() for possible id values.
     *  - 'to':
     *     The address or addresses the message will be sent to. The
     *     formatting of this string must comply with RFC 2822.
     *  - 'from':
     *     The address the message will be marked as being from, which is
     *     either a custom address or the site-wide default email address.
     *  - 'subject':
     *     Subject of the email to be sent. This must not contain any newline
     *     characters, or the email may not be sent properly.
     *  - 'body':
     *     An array of strings containing the message text. The message body is
     *     created by concatenating the individual array strings into a single text
     *     string using "\n\n" as a separator.
     *  - 'headers':
     *     Associative array containing mail headers, such as From, Sender,
     *     MIME-Version, Content-Type, etc.
     *  - 'params':
     *     An array of optional parameters supplied by the caller of drupal_mail()
     *     that is used to build the message before hook_mail_alter() is invoked.
     *  - 'language':
     *     The language object used to build the message before hook_mail_alter()
     *     is invoked.
     *
     * @see drupal_mail()
     */
    function hook_mail_alter(&$message) {
      if ($message['id'] == 'modulename_messagekey') {
        $message['body'][] = "--\nMail sent out from " . variable_get('sitename', t('Drupal'));
      }
    }
    
    /**
     * Alter the information parsed from module and theme .info files
     *
     * This hook is invoked in _system_rebuild_module_data() and in
     * _system_rebuild_theme_data(). A module may implement this hook in order to
     * add to or alter the data generated by reading the .info file with
     * drupal_parse_info_file().
     *
     * @param &$info
     *   The .info file contents, passed by reference so that it can be altered.
     * @param $file
     *   Full information about the module or theme, including $file->name, and
     *   $file->filename
     * @param $type
     *   Either 'module' or 'theme', depending on the type of .info file that was
     *   passed.
     */
    function hook_system_info_alter(&$info, $file, $type) {
      // Only fill this in if the .info file does not define a 'datestamp'.
      if (empty($info['datestamp'])) {
        $info['datestamp'] = filemtime($file->filename);
      }
    }
    
    /**
     * Define user permissions.
     *
     * This hook can supply permissions that the module defines, so that they
     * can be selected on the user permissions page and used to grant or restrict
     * access to actions the module performs.
     *
     * Permissions are checked using user_access().
     *
     * For a detailed usage example, see page_example.module.
     *
     * @return
     *   An array of which permission names are the keys and their corresponding
     *   values are descriptions of each permission.
     *   The permission names (keys of the array) must not be wrapped with
     *   the t() function, since the string extractor takes care of
     *   extracting permission names defined in the perm hook for
     *   translation. The permission descriptions (values of the array)
     *   should be wrapped in the t() function so they can be translated.
     */
    function hook_permission() {
      return array(
        'administer my module' =>  array(
          'title' => t('Administer my module'),
          'description' => t('Perform administration tasks for my module.'),
        ),
      );
    }
    
    /**
     * Register a module (or theme's) theme implementations.
     *
     * Modules and themes implementing this return an array of arrays. The key
     * to each sub-array is the internal name of the hook, and the array contains
     * info about the hook. Each array may contain the following items:
     *
     * - variables: (required if "render element" not present) An array of
     *   variables that this theme hook uses. This value allows the theme layer to
     *   properly utilize templates. Each array key represents the name of the
     *   variable and the value will be used as the default value if it is not given
     *   when theme() is called. Template implementations receive these arguments as
     *   variables in the template file. Function implementations are passed this
     *   array data in the $variables parameter.
     * - render element: (required if "variables" not present) A string that is the
     *   name of the sole renderable element to pass to the theme function. The
     *   string represents the name of the "variable" that will hold the renderable
     *   array inside any optional preprocess or process functions. Cannot be used
     *   with the "variables" item; only one or the other, not both, can be present
     *   in a hook's info array.
     * - file: The file the implementation resides in. This file will be included
     *   prior to the theme being rendered, to make sure that the function or
     *   preprocess function (as needed) is actually loaded; this makes it possible
     *   to split theme functions out into separate files quite easily.
     * - path: Override the path of the file to be used. Ordinarily the module or
     *   theme path will be used, but if the file will not be in the default path,
     *   include it here. This path should be relative to the Drupal root
     *   directory.
     * - template: If specified, this theme implementation is a template, and this
     *   is the template file <b>without an extension</b>. Do not put .tpl.php
     *   on this file; that extension will be added automatically by the default
     *   rendering engine (which is PHPTemplate). If 'path', above, is specified,
     *   the template should also be in this path.
     * - function: If specified, this will be the function name to invoke for this
     *   implementation. If neither file nor function is specified, a default
     *   function name will be assumed. For example, if a module registers
     *   the 'node' theme hook, 'theme_node' will be assigned to its function.
     *   If the chameleon theme registers the node hook, it will be assigned
     *   'chameleon_node' as its function.
     * - pattern: A regular expression pattern to be used to allow this theme
     *   implementation to have a dynamic name. The convention is to use __ to
     *   differentiate the dynamic portion of the theme. For example, to allow
     *   forums to be themed individually, the pattern might be: 'forum__'. Then,
     *   when the forum is themed, call: <code>theme(array('forum__' . $tid, 'forum'),
     *   $forum)</code>.
     * - preprocess functions: A list of functions used to preprocess this data.
     *   Ordinarily this won't be used; it's automatically filled in. By default,
     *   for a module this will be filled in as template_preprocess_HOOK. For
     *   a theme this will be filled in as phptemplate_preprocess and
     *   phptemplate_preprocess_HOOK as well as themename_preprocess and
     *   themename_preprocess_HOOK.
     * - override preprocess functions: Set to TRUE when a theme does NOT want the
     *   standard preprocess functions to run. This can be used to give a theme
     *   FULL control over how variables are set. For example, if a theme wants
     *   total control over how certain variables in the page.tpl.php are set,
     *   this can be set to true. Please keep in mind that when this is used
     *   by a theme, that theme becomes responsible for making sure necessary
     *   variables are set.
     * - type: (automatically derived) Where the theme hook is defined:
     *   'module', 'theme_engine', or 'theme'.
     * - theme path: (automatically derived) The directory path of the theme or
     *   module, so that it doesn't need to be looked up.
     *
     * The following parameters are all optional.
     *
     * @param $existing
     *   An array of existing implementations that may be used for override
     *   purposes. This is primarily useful for themes that may wish to examine
     *   existing implementations to extract data (such as arguments) so that
     *   it may properly register its own, higher priority implementations.
     * @param $type
     *   What 'type' is being processed. This is primarily useful so that themes
     *   tell if they are the actual theme being called or a parent theme.
     *   May be one of:
     *     - module: A module is being checked for theme implementations.
     *     - base_theme_engine: A theme engine is being checked for a theme which is a parent of the actual theme being used.
     *     - theme_engine: A theme engine is being checked for the actual theme being used.
     *     - base_theme: A base theme is being checked for theme implementations.
     *     - theme: The actual theme in use is being checked.
     * @param $theme
     *   The actual name of theme that is being being checked (mostly only useful for
     *   theme engine).
     * @param $path
     *   The directory path of the theme or module, so that it doesn't need to be
     *   looked up.
     *
     * @return
     *   A keyed array of theme hooks.
     */
    function hook_theme($existing, $type, $theme, $path) {
      return array(
        'forum_display' => array(
          'variables' => array('forums' => NULL, 'topics' => NULL, 'parents' => NULL, 'tid' => NULL, 'sortby' => NULL, 'forum_per_page' => NULL),
        ),
        'forum_list' => array(
          'variables' => array('forums' => NULL, 'parents' => NULL, 'tid' => NULL),
        ),
        'forum_topic_list' => array(
          'variables' => array('tid' => NULL, 'topics' => NULL, 'sortby' => NULL, 'forum_per_page' => NULL),
        ),
        'forum_icon' => array(
          'variables' => array('new_posts' => NULL, 'num_posts' => 0, 'comment_mode' => 0, 'sticky' => 0),
        ),
        'status_report' => array(
          'render element' => 'requirements',
          'file' => 'system.admin.inc',
        ),
        'system_date_time_settings' => array(
          'render element' => 'form',
          'file' => 'system.admin.inc',
        ),
      );
    }
    
    /**
     * Alter the theme registry information returned from hook_theme().
     *
     * The theme registry stores information about all available theme hooks,
     * including which callback functions those hooks will call when triggered,
     * what template files are exposed by these hooks, and so on.
     *
     * Note that this hook is only executed as the theme cache is re-built.
     * Changes here will not be visible until the next cache clear.
     *
     * The $theme_registry array is keyed by theme hook name, and contains the
     * information returned from hook_theme(), as well as additional properties
     * added by _theme_process_registry().
     *
     * For example:
     * @code
     *  $theme_registry['user_profile'] = array(
     *    'variables' => array(
     *      'account' => NULL,
     *    ),
     *    'template' => 'modules/user/user-profile',
     *    'file' => 'modules/user/user.pages.inc',
     *    'type' => 'module',
     *    'theme path' => 'modules/user',
     *    'preprocess functions' => array(
     *      0 => 'template_preprocess',
     *      1 => 'template_preprocess_user_profile',
     *     ),
     *   )
     * );
     * @endcode
     *
     * @param $theme_registry
     *   The entire cache of theme registry information, post-processing.
     * @see hook_theme()
     * @see _theme_process_registry()
     */
    function hook_theme_registry_alter(&$theme_registry) {
      // Kill the next/previous forum topic navigation links.
      foreach ($theme_registry['forum_topic_navigation']['preprocess functions'] as $key => $value) {
        if ($value = 'template_preprocess_forum_topic_navigation') {
          unset($theme_registry['forum_topic_navigation']['preprocess functions'][$key]);
        }
      }
    }
    
    /**
     * Return the machine-readable name of the theme to use for the current page.
     *
     * This hook can be used to dynamically set the theme for the current page
     * request. It overrides the default theme as well as any per-page or
     * per-section theme set by the theme callback function in hook_menu(). This
     * should be used by modules which need to override the theme based on dynamic
     * conditions.
     *
     * Since only one theme can be used at a time, the last (i.e., highest
     * weighted) module which returns a valid theme name from this hook will
     * prevail.
     *
     * @return
     *   The machine-readable name of the theme that should be used for the current
     *   page request. The value returned from this function will only have an
     *   effect if it corresponds to a currently-active theme on the site.
     */
    function hook_custom_theme() {
      // Allow the user to request a particular theme via a query parameter.
      if (isset($_GET['theme'])) {
        return $_GET['theme'];
      }
    }
    
    /**
     * Register XML-RPC callbacks.
     *
     * This hook lets a module register callback functions to be called when
     * particular XML-RPC methods are invoked by a client.
     *
     * @return
     *   An array which maps XML-RPC methods to Drupal functions. Each array
     *   element is either a pair of method => function or an array with four
     *   entries:
     *   - The XML-RPC method name (for example, module.function).
     *   - The Drupal callback function (for example, module_function).
     *   - The method signature is an array of XML-RPC types. The first element
     *     of this array is the type of return value and then you should write a
     *     list of the types of the parameters. XML-RPC types are the following
     *     (See the types at http://www.xmlrpc.com/spec):
     *       - "boolean": 0 (false) or 1 (true).
     *       - "double": a floating point number (for example, -12.214).
     *       - "int": a integer number (for example,  -12).
     *       - "array": an array without keys (for example, array(1, 2, 3)).
     *       - "struct": an associative array or an object (for example,
     *          array('one' => 1, 'two' => 2)).
     *       - "date": when you return a date, then you may either return a
     *          timestamp (time(), mktime() etc.) or an ISO8601 timestamp. When
     *          date is specified as an input parameter, then you get an object,
     *          which is described in the function xmlrpc_date
     *       - "base64": a string containing binary data, automatically
     *          encoded/decoded automatically.
     *       - "string": anything else, typically a string.
     *   - A descriptive help string, enclosed in a t() function for translation
     *     purposes.
     *   Both forms are shown in the example.
     */
    function hook_xmlrpc() {
      return array(
        'drupal.login' => 'drupal_login',
        array(
          'drupal.site.ping',
          'drupal_directory_ping',
          array('boolean', 'string', 'string', 'string', 'string', 'string'),
          t('Handling ping request'))
      );
    }
    
    /**
     * Alter the definition of XML-RPC methods before they are called.
     *
     * This hook lets at module modify the callback definition for already
     * declared XML-RPC methods, when they are being invoked by a client.
     *
     * This hook is invoked by xmlrpc.php. The method definitions are
     * passed in by reference. Each element of the $methods array is one
     * callback definition returned by a module from hook_xmlrpc. Additional
     * methods may be added, or existing items altered.
     *
     * Modules implementing this hook must take care of the fact that
     * hook_xmlrpc allows two distinct and incompatible formats for callback
     * definition, so module must be prepared to handle either format for
     * each callback being altered.
     *
     * @see hook_xmlrpc()
     *
     * @param $methods
     *   Associative array of method callback definitions returned from
     *   hook_xmlrpc.
     */
    function hook_xmlrpc_alter(&$methods) {
    
      // Direct update for methods defined the simple way
      $methods['drupal.login'] = 'mymodule_login';
    
      // Lookup update for methods defined the complex way
      foreach ($methods as $key => &$method) {
        if (!is_int($key)) {
          continue;
        }
        if ($method[0] == 'drupal.site.ping') {
          $method[1] = 'mymodule_directory_ping';
        }
      }
    }
    
    /**
     * Log an event message
     *
     * This hook allows modules to route log events to custom destinations, such as
     * SMS, Email, pager, syslog, ...etc.
     *
     * @param $log_entry
     *   An associative array containing the following keys:
     *   - type: The type of message for this entry. For contributed modules, this is
     *     normally the module name. Do not use 'debug', use severity WATCHDOG_DEBUG instead.
     *   - user: The user object for the user who was logged in when the event happened.
     *   - request_uri: The Request URI for the page the event happened in.
     *   - referer: The page that referred the use to the page where the event occurred.
     *   - ip: The IP address where the request for the page came from.
     *   - timestamp: The UNIX timestamp of the date/time the event occurred
     *   - severity: One of the following values as defined in RFC 3164 http://www.faqs.org/rfcs/rfc3164.html
     *     WATCHDOG_EMERG     Emergency: system is unusable
     *     WATCHDOG_ALERT     Alert: action must be taken immediately
     *     WATCHDOG_CRITICAL  Critical: critical conditions
     *     WATCHDOG_ERROR     Error: error conditions
     *     WATCHDOG_WARNING   Warning: warning conditions
     *     WATCHDOG_NOTICE    Notice: normal but significant condition
     *     WATCHDOG_INFO      Informational: informational messages
     *     WATCHDOG_DEBUG     Debug: debug-level messages
     *   - link: an optional link provided by the module that called the watchdog() function.
     *   - message: The text of the message to be logged.
     */
    function hook_watchdog(array $log_entry) {
      global $base_url, $language;
    
      $severity_list = array(
        WATCHDOG_EMERG    => t('Emergency'),
        WATCHDOG_ALERT    => t('Alert'),
        WATCHDOG_CRITICAL => t('Critical'),
        WATCHDOG_ERROR    => t('Error'),
        WATCHDOG_WARNING  => t('Warning'),
        WATCHDOG_NOTICE   => t('Notice'),
        WATCHDOG_INFO     => t('Info'),
        WATCHDOG_DEBUG    => t('Debug'),
      );
    
      $to = 'someone@example.com';
      $params = array();
      $params['subject'] = t('[@site_name] @severity_desc: Alert from your web site', array(
        '@site_name' => variable_get('site_name', 'Drupal'),
        '@severity_desc' => $severity_list[$log_entry['severity']],
      ));
    
      $params['message']  = "\nSite:         @base_url";
      $params['message'] .= "\nSeverity:     (@severity) @severity_desc";
      $params['message'] .= "\nTimestamp:    @timestamp";
      $params['message'] .= "\nType:         @type";
      $params['message'] .= "\nIP Address:   @ip";
      $params['message'] .= "\nRequest URI:  @request_uri";
      $params['message'] .= "\nReferrer URI: @referer_uri";
      $params['message'] .= "\nUser:         (@uid) @name";
      $params['message'] .= "\nLink:         @link";
      $params['message'] .= "\nMessage:      \n\n@message";
    
      $params['message'] = t($params['message'], array(
        '@base_url'      => $base_url,
        '@severity'      => $log_entry['severity'],
        '@severity_desc' => $severity_list[$log_entry['severity']],
        '@timestamp'     => format_date($log_entry['timestamp']),
        '@type'          => $log_entry['type'],
        '@ip'            => $log_entry['ip'],
        '@request_uri'   => $log_entry['request_uri'],
        '@referer_uri'   => $log_entry['referer'],
        '@uid'           => $log_entry['user']->uid,
        '@name'          => $log_entry['user']->name,
        '@link'          => strip_tags($log_entry['link']),
        '@message'       => strip_tags($log_entry['message']),
      ));
    
      drupal_mail('emaillog', 'entry', $to, $language, $params);
    }
    
    /**
     * Prepare a message based on parameters; called from drupal_mail().
     *
     * @param $key
     *   An identifier of the mail.
     * @param $message
     *  An array to be filled in. Keys in this array include:
     *  - 'id':
     *     An id to identify the mail sent. Look at module source code
     *     or drupal_mail() for possible id values.
     *  - 'to':
     *     The address or addresses the message will be sent to. The
     *     formatting of this string must comply with RFC 2822.
     *  - 'subject':
     *     Subject of the e-mail to be sent. This must not contain any newline
     *     characters, or the mail may not be sent properly. drupal_mail() sets
     *     this to an empty string when the hook is invoked.
     *  - 'body':
     *     An array of lines containing the message to be sent. Drupal will format
     *     the correct line endings for you. drupal_mail() sets this to an empty
     *     array when the hook is invoked.
     *  - 'from':
     *     The address the message will be marked as being from, which is
     *     set by drupal_mail() to either a custom address or the site-wide
     *     default email address when the hook is invoked.
     *  - 'headers':
     *     Associative array containing mail headers, such as From, Sender,
     *     MIME-Version, Content-Type, etc. drupal_mail() pre-fills
     *     several headers in this array.
     * @param $params
     *   An array of parameters supplied by the caller of drupal_mail().
     */
    function hook_mail($key, &$message, $params) {
      $account = $params['account'];
      $context = $params['context'];
      $variables = array(
        '%site_name' => variable_get('site_name', 'Drupal'),
        '%username' => format_username($account),
      );
      if ($context['hook'] == 'taxonomy') {
        $entity = $params['object'];
        $vocabulary = taxonomy_vocabulary_load($entity->vid);
        $variables += array(
          '%term_name' => $entity->name,
          '%term_description' => $entity->description,
          '%term_id' => $entity->tid,
          '%vocabulary_name' => $vocabulary->name,
          '%vocabulary_description' => $vocabulary->description,
          '%vocabulary_id' => $vocabulary->vid,
        );
      }
    
      // Node-based variable translation is only available if we have a node.
      if (isset($params['node'])) {
        $node = $params['node'];
        $variables += array(
          '%uid' => $node->uid,
          '%node_url' => url('node/' . $node->nid, array('absolute' => TRUE)),
          '%node_type' => node_type_get_name($node),
          '%title' => $node->title,
          '%teaser' => $node->teaser,
          '%body' => $node->body,
        );
      }
      $subject = strtr($context['subject'], $variables);
      $body = strtr($context['message'], $variables);
      $message['subject'] .= str_replace(array("\r", "\n"), '', $subject);
      $message['body'][] = drupal_html_to_text($body);
    }
    
    /**
     * Add a list of cache tables to be cleared.
     *
     * This hook allows your module to add cache table names to the list of cache
     * tables that will be cleared by the Clear button on the Performance page or
     * whenever drupal_flush_all_caches is invoked.
     *
     * @see drupal_flush_all_caches()
     *
     * @return
     *   An array of cache table names.
     */
    function hook_flush_caches() {
      return array('cache_example');
    }
    
    /**
     * Perform necessary actions after modules are installed.
     *
     * This function differs from hook_install() as it gives all other
     * modules a chance to perform actions when a module is installed,
     * whereas hook_install() will only be called on the module actually
     * being installed.
     *
     * @see hook_install()
     *
     * @param $modules
     *   An array of the installed modules.
     */
    function hook_modules_installed($modules) {
      if (in_array('lousy_module', $modules)) {
        variable_set('lousy_module_conflicting_variable', FALSE);
      }
    }
    
    /**
     * Perform necessary actions after modules are enabled.
     *
     * This function differs from hook_enable() as it gives all other
     * modules a chance to perform actions when modules are enabled,
     * whereas hook_enable() will only be called on the module actually
     * being enabled.
     *
     * @see hook_enable()
     *
     * @param $modules
     *   An array of the enabled modules.
     */
    function hook_modules_enabled($modules) {
      if (in_array('lousy_module', $modules)) {
        drupal_set_message(t('mymodule is not compatible with lousy_module'), 'error');
        mymodule_disable_functionality();
      }
    }
    
    /**
     * Perform necessary actions after modules are disabled.
     *
     * This function differs from hook_disable() as it gives all other
     * modules a chance to perform actions when modules are disabled,
     * whereas hook_disable() will only be called on the module actually
     * being disabled.
     *
     * @see hook_disable()
     *
     * @param $modules
     *   An array of the disabled modules.
     */
    function hook_modules_disabled($modules) {
      if (in_array('lousy_module', $modules)) {
        mymodule_enable_functionality();
      }
    }
    
    /**
     * Perform necessary actions after modules are uninstalled.
     *
     * This function differs from hook_uninstall() as it gives all other
     * modules a chance to perform actions when a module is uninstalled,
     * whereas hook_uninstall() will only be called on the module actually
     * being uninstalled.
     *
     * It is recommended that you implement this module if your module
     * stores data that may have been set by other modules.
     *
     * @see hook_uninstall()
     *
     * @param $modules
     *   An array of the uninstalled modules.
     */
    function hook_modules_uninstalled($modules) {
      foreach ($modules as $module) {
        db_delete('mymodule_table')
          ->condition('module', $module)
          ->execute();
      }
      mymodule_cache_rebuild();
    }
    
    /**
     * Registers PHP stream wrapper implementations associated with a module.
     *
     * Provide a facility for managing and querying user-defined stream wrappers
     * in PHP. PHP's internal stream_get_wrappers() doesn't return the class
     * registered to handle a stream, which we need to be able to find the handler
     * for class instantiation.
     *
     * If a module registers a scheme that is already registered with PHP, it will
     * be unregistered and replaced with the specified class.
     *
     * @return
     *   A nested array, keyed first by scheme name ("public" for "public://"),
     *   then keyed by the following values:
     *   - 'name' A short string to name the wrapper.
     *   - 'class' A string specifying the PHP class that implements the
     *     DrupalStreamWrapperInterface interface.
     *   - 'description' A string with a short description of what the wrapper does.
     *   - 'type' A bitmask of flags indicating what type of streams this wrapper
     *     will access - local or remote, readable and/or writeable, etc. Many
     *     shortcut constants are defined in stream_wrappers.inc. 
     *
     * @see file_get_stream_wrappers()
     * @see hook_stream_wrappers_alter()
     * @see system_stream_wrappers()
     */
    function hook_stream_wrappers() {
      return array(
        'public' => array(
          'name' => t('Public files'),
          'class' => 'DrupalPublicStreamWrapper',
          'description' => t('Public local files served by the webserver.'),
        ),
        'private' => array(
          'name' => t('Private files'),
          'class' => 'DrupalPrivateStreamWrapper',
          'description' => t('Private local files served by Drupal.'),
        ),
        'temp' => array(
          'name' => t('Temporary files'),
          'class' => 'DrupalTempStreamWrapper',
          'description' => t('Temporary local files for upload and previews.'),
          'type' => STREAM_WRAPPERS_HIDDEN,
        )
      );
    }
    
    /**
     * Alters the list of PHP stream wrapper implementations.
     *
     * @see file_get_stream_wrappers()
     * @see hook_stream_wrappers()
     */
    function hook_stream_wrappers_alter(&$wrappers) {
      // Change the name of private files to reflect the performance.
      $wrappers['private']['name'] = t('Slow files');
    }
    
    /**
     * Load additional information into file objects.
     *
     * file_load_multiple() calls this hook to allow modules to load
     * additional information into each file.
     *
     * @param $files
     *   An array of file objects, indexed by fid.
     *
     * @see file_load_multiple()
     * @see upload_file_load()
     */
    function hook_file_load($files) {
      // Add the upload specific data into the file object.
      $result = db_query('SELECT * FROM {upload} u WHERE u.fid IN (:fids)', array(':fids' => array_keys($files)))->fetchAll(PDO::FETCH_ASSOC);
      foreach ($result as $record) {
        foreach ($record as $key => $value) {
          $files[$record['fid']]->$key = $value;
        }
      }
    }
    
    /**
     * Check that files meet a given criteria.
     *
     * This hook lets modules perform additional validation on files. They're able
     * to report a failure by returning one or more error messages.
     *
     * @param $file
     *   The file object being validated.
     * @return
     *   An array of error messages. If there are no problems with the file return
     *   an empty array.
     *
     * @see file_validate()
     */
    function hook_file_validate(&$file) {
      $errors = array();
    
      if (empty($file->filename)) {
        $errors[] = t("The file's name is empty. Please give a name to the file.");
      }
      if (strlen($file->filename) > 255) {
        $errors[] = t("The file's name exceeds the 255 characters limit. Please rename the file and try again.");
      }
    
      return $errors;
    }
    
    /**
     * Respond to a file being added.
     *
     * This hook is called when a file has been added to the database. The hook
     * doesn't distinguish between files created as a result of a copy or those
     * created by an upload.
     *
     * @param $file
     *   The file that has just been created.
     *
     * @see file_save()
     */
    function hook_file_insert(&$file) {
    
    }
    
    /**
     * Respond to a file being updated.
     *
     * This hook is called when file_save() is called on an existing file.
     *
     * @param $file
     *   The file that has just been updated.
     *
     * @see file_save()
     */
    function hook_file_update(&$file) {
    
    }
    
    /**
     * Respond to a file that has been copied.
     *
     * @param $file
     *   The newly copied file object.
     * @param $source
     *   The original file before the copy.
     *
     * @see file_copy()
     */
    function hook_file_copy($file, $source) {
    
    }
    
    /**
     * Respond to a file that has been moved.
     *
     * @param $file
     *   The updated file object after the move.
     * @param $source
     *   The original file object before the move.
     *
     * @see file_move()
     */
    function hook_file_move($file, $source) {
    
    }
    
    /**
     * Report the number of times a file is referenced by a module.
     *
     * This hook is called to determine if a files is in use. Multiple modules may
     * be referencing the same file and to prevent one from deleting a file used by
     * another this hook is called.
     *
     * @param $file
     *   The file object being checked for references.
     * @return
     *   If the module uses this file return an array with the module name as the
     *   key and the value the number of times the file is used.
     *
     * @see file_delete()
     * @see upload_file_references()
     */
    function hook_file_references($file) {
      // If upload.module is still using a file, do not let other modules delete it.
      $file_used = (bool) db_query_range('SELECT 1 FROM {upload} WHERE fid = :fid', 0, 1, array(':fid' => $file->fid))->fetchField();
      if ($file_used) {
        // Return the name of the module and how many references it has to the file.
        return array('upload' => $count);
      }
    }
    
    /**
     * Respond to a file being deleted.
     *
     * @param $file
     *   The file that has just been deleted.
     *
     * @see file_delete()
     * @see upload_file_delete()
     */
    function hook_file_delete($file) {
      // Delete all information associated with the file.
      db_delete('upload')->condition('fid', $file->fid)->execute();
    }
    
    /**
     * Control access to private file downloads and specify HTTP headers.
     *
     * This hook allows modules enforce permissions on file downloads when the
     * private file download method is selected. Modules can also provide headers
     * to specify information like the file's name or MIME type.
     *
     * @param $uri
     *   The URI of the file.
     * @return
     *   If the user does not have permission to access the file, return -1. If the
     *   user has permission, return an array with the appropriate headers. If the
     *   file is not controlled by the current module, the return value should be
     *   NULL.
     *
     * @see file_download()
     * @see upload_file_download()
     */
    function hook_file_download($uri) {
      // Check if the file is controlled by the current module.
      if (!file_prepare_directory($uri)) {
        $uri = FALSE;
      }
      $result = db_query("SELECT f.* FROM {file} f INNER JOIN {upload} u ON f.fid = u.fid WHERE uri = :uri", array('uri' => $uri));
      foreach ($result as $file) {
        if (!user_access('view uploaded files')) {
          return -1;
        }
        return array(
          'Content-Type' => $file->filemime,
          'Content-Length' => $file->filesize,
        );
      }
    }
    
    /**
     * Alter the URL to a file.
     *
     * This hook is called from file_create_url(), and  is called fairly
     * frequently (10+ times per page), depending on how many files there are in a
     * given page.
     * If CSS and JS aggregation are disabled, this can become very frequently
     * (50+ times per page) so performance is critical.
     *
     * This function should alter the URI, if it wants to rewrite the file URL.
     *
     * @param $uri
     *   The URI to a file for which we need an external URL, or the path to a
     *   shipped file.
     */
    function hook_file_url_alter(&$uri) {
      global $user;
    
      // User 1 will always see the local file in this example.
      if ($user->uid == 1) {
        return;
      }
    
      $cdn1 = 'http://cdn1.example.com';
      $cdn2 = 'http://cdn2.example.com';
      $cdn_extensions = array('css', 'js', 'gif', 'jpg', 'jpeg', 'png');
    
      // Most CDNs don't support private file transfers without a lot of hassle,
      // so don't support this in the common case.
      $schemes = array('public');
    
      $scheme = file_uri_scheme($uri);
    
      // Only serve shipped files and public created files from the CDN.
      if (!$scheme || in_array($scheme, $schemes)) {
        // Shipped files.
        if (!$scheme) {
          $path = $uri;
        }
        // Public created files.
        else {
          $wrapper = file_stream_wrapper_get_instance_by_scheme($scheme);
          $path = $wrapper->getDirectoryPath() . '/' . file_uri_target($uri);
        }
    
        // Clean up Windows paths.
        $path = str_replace('\\', '/', $path);
    
        // Serve files with one of the CDN extensions from CDN 1, all others from
        // CDN 2.
        $pathinfo = pathinfo($path);
        if (array_key_exists('extension', $pathinfo) && in_array($pathinfo['extension'], $cdn_extensions)) {
          $uri = $cdn1 . '/' . $path;
        }
        else {
          $uri = $cdn2 . '/' . $path;
        }
      }
    }
                                                                                                          /**
     * Check installation requirements and do status reporting.
     *
     * This hook has two closely related uses, determined by the $phase argument:
     * checking installation requirements ($phase == 'install')
     * and status reporting ($phase == 'runtime').
     *
     * Note that this hook, like all others dealing with installation and updates,
     * must reside in a module_name.install file, or it will not properly abort
     * the installation of the module if a critical requirement is missing.
     *
     * During the 'install' phase, modules can for example assert that
     * library or server versions are available or sufficient.
     * Note that the installation of a module can happen during installation of
     * Drupal itself (by install.php) with an installation profile or later by hand.
     * As a consequence, install-time requirements must be checked without access
     * to the full Drupal API, because it is not available during install.php.
     * For localization you should for example use $t = get_t() to
     * retrieve the appropriate localization function name (t() or st()).
     * If a requirement has a severity of REQUIREMENT_ERROR, install.php will abort
     * or at least the module will not install.
     * Other severity levels have no effect on the installation.
     * Module dependencies do not belong to these installation requirements,
     * but should be defined in the module's .info file.
     *
     * The 'runtime' phase is not limited to pure installation requirements
     * but can also be used for more general status information like maintenance
     * tasks and security issues.
     * The returned 'requirements' will be listed on the status report in the
     * administration section, with indication of the severity level.
     * Moreover, any requirement with a severity of REQUIREMENT_ERROR severity will
     * result in a notice on the the administration overview page.
     *
     * @param $phase
     *   The phase in which hook_requirements is run:
     *   - 'install': the module is being installed.
     *   - 'runtime': the runtime requirements are being checked and shown on the
     *              status report page.
     *
     * @return
     *   A keyed array of requirements. Each requirement is itself an array with
     *   the following items:
     *     - 'title': the name of the requirement.
     *     - 'value': the current value (e.g. version, time, level, ...). During
     *       install phase, this should only be used for version numbers, do not set
     *       it if not applicable.
     *     - 'description': description of the requirement/status.
     *     - 'severity': the requirement's result/severity level, one of:
     *         - REQUIREMENT_INFO:    For info only.
     *         - REQUIREMENT_OK:      The requirement is satisfied.
     *         - REQUIREMENT_WARNING: The requirement failed with a warning.
     *         - REQUIREMENT_ERROR:   The requirement failed with an error.
     */
    function hook_requirements($phase) {
      $requirements = array();
      // Ensure translations don't break at install time
      $t = get_t();
    
      // Report Drupal version
      if ($phase == 'runtime') {
        $requirements['drupal'] = array(
          'title' => $t('Drupal'),
          'value' => VERSION,
          'severity' => REQUIREMENT_INFO
        );
      }
    
      // Test PHP version
      $requirements['php'] = array(
        'title' => $t('PHP'),
        'value' => ($phase == 'runtime') ? l(phpversion(), 'admin/logs/status/php') : phpversion(),
      );
      if (version_compare(phpversion(), DRUPAL_MINIMUM_PHP) < 0) {
        $requirements['php']['description'] = $t('Your PHP installation is too old. Drupal requires at least PHP %version.', array('%version' => DRUPAL_MINIMUM_PHP));
        $requirements['php']['severity'] = REQUIREMENT_ERROR;
      }
    
      // Report cron status
      if ($phase == 'runtime') {
        $cron_last = variable_get('cron_last');
    
        if (is_numeric($cron_last)) {
          $requirements['cron']['value'] = $t('Last run !time ago', array('!time' => format_interval(REQUEST_TIME - $cron_last)));
        }
        else {
          $requirements['cron'] = array(
            'description' => $t('Cron has not run. It appears cron jobs have not been setup on your system. Check the help pages for <a href="@url">configuring cron jobs</a>.', array('@url' => 'http://drupal.org/cron')),
            'severity' => REQUIREMENT_ERROR,
            'value' => $t('Never run'),
          );
        }
    
        $requirements['cron']['description'] .= ' ' . t('You can <a href="@cron">run cron manually</a>.', array('@cron' => url('admin/logs/status/run-cron')));
    
        $requirements['cron']['title'] = $t('Cron maintenance tasks');
      }
    
      return $requirements;
    }
    
    /**
     * Define the current version of the database schema.
     *
     * A Drupal schema definition is an array structure representing one or
     * more tables and their related keys and indexes. A schema is defined by
     * hook_schema() which must live in your module's .install file.
     *
     * By implementing hook_schema() and specifying the tables your module
     * declares, you can easily create and drop these tables on all
     * supported database engines. You don't have to deal with the
     * different SQL dialects for table creation and alteration of the
     * supported database engines.
     *
     * See the Schema API Handbook at http://drupal.org/node/146843 for
     * details on schema definition structures.
     *
     * @return
     * A schema definition structure array. For each element of the
     * array, the key is a table name and the value is a table structure
     * definition.
     */
    function hook_schema() {
      $schema['node'] = array(
        // example (partial) specification for table "node"
        'description' => 'The base table for nodes.',
        'fields' => array(
          'nid' => array(
            'description' => 'The primary identifier for a node.',
            'type' => 'serial',
            'unsigned' => TRUE,
            'not null' => TRUE),
          'vid' => array(
            'description' => 'The current {node_revision}.vid version identifier.',
            'type' => 'int',
            'unsigned' => TRUE,
            'not null' => TRUE,
            'default' => 0),
          'type' => array(
            'description' => 'The {node_type} of this node.',
            'type' => 'varchar',
            'length' => 32,
            'not null' => TRUE,
            'default' => ''),
          'title' => array(
            'description' => 'The title of this node, always treated a non-markup plain text.',
            'type' => 'varchar',
            'length' => 255,
            'not null' => TRUE,
            'default' => ''),
          ),
        'indexes' => array(
          'node_changed'        => array('changed'),
          'node_created'        => array('created'),
          ),
        'unique keys' => array(
          'nid_vid' => array('nid', 'vid'),
          'vid'     => array('vid')
          ),
        'primary key' => array('nid'),
      );
      return $schema;
    }
    
    /**
     * Perform alterations to existing database schemas.
     *
     * When a module modifies the database structure of another module (by
     * changing, adding or removing fields, keys or indexes), it should
     * implement hook_schema_alter() to update the default $schema to take
     * it's changes into account.
     *
     * See hook_schema() for details on the schema definition structure.
     *
     * @param $schema
     *   Nested array describing the schemas for all modules.
     */
    function hook_schema_alter(&$schema) {
      // Add field to existing schema.
      $schema['users']['fields']['timezone_id'] = array(
        'type' => 'int',
        'not null' => TRUE,
        'default' => 0,
        'description' => 'Per-user timezone configuration.',
      );
    }
    
    /**
     * Perform alterations to a structured query.
     *
     * Structured (aka dynamic) queries that have tags associated may be altered by any module
     * before the query is executed.
     *
     * @see hook_query_TAG_alter()
     * @see node_query_node_access_alter()
     * @see QueryAlterableInterface
     * @see SelectQueryInterface
     * @param $query
     *   A Query object describing the composite parts of a SQL query.
     */
    function hook_query_alter(QueryAlterableInterface $query) {
      if ($query->hasTag('micro_limit')) {
        $query->range(0, 2);
      }
    }
    
    /**
     * Perform alterations to a structured query for a given tag.
     *
     * @see hook_query_alter()
     * @see node_query_node_access_alter()
     * @see QueryAlterableInterface
     * @see SelectQueryInterface
     *
     * @param $query
     *   An Query object describing the composite parts of a SQL query.
     */
    function hook_query_TAG_alter(QueryAlterableInterface $query) {
      // Skip the extra expensive alterations if site has no node access control modules.
      if (!node_access_view_all_nodes()) {
        // Prevent duplicates records.
        $query->distinct();
        // The recognized operations are 'view', 'update', 'delete'.
        if (!$op = $query->getMetaData('op')) {
          $op = 'view';
        }
        // Skip the extra joins and conditions for node admins.
        if (!user_access('bypass node access')) {
          // The node_access table has the access grants for any given node.
          $access_alias = $query->join('node_access', 'na', 'na.nid = n.nid');
          $or = db_or();
          // If any grant exists for the specified user, then user has access to the node for the specified operation.
          foreach (node_access_grants($op, $query->getMetaData('account')) as $realm => $gids) {
            foreach ($gids as $gid) {
              $or->condition(db_and()
                ->condition("{$access_alias}.gid", $gid)
                ->condition("{$access_alias}.realm", $realm)
              );
            }
          }
    
          if (count($or->conditions())) {
            $query->condition($or);
          }
    
          $query->condition("{$access_alias}.grant_$op", 1, '>=');
        }
      }
    }
    
    /**
     * Perform setup tasks when the module is installed.
     *
     * If the module implements hook_schema(), the database tables will
     * be created before this hook is fired.
     *
     * The hook will be called the first time a module is installed, and the
     * module's schema version will be set to the module's greatest numbered update
     * hook. Because of this, anytime a hook_update_N() is added to the module, this
     * function needs to be updated to reflect the current version of the database
     * schema.
     *
     * See the Schema API documentation at
     * @link http://drupal.org/node/146843 http://drupal.org/node/146843 @endlink
     * for details on hook_schema and how database tables are defined.
     *
     * Note that since this function is called from a full bootstrap, all functions
     * (including those in modules enabled by the current page request) are
     * available when this hook is called. Use cases could be displaying a user
     * message, or calling a module function necessary for initial setup, etc.
     *
     * Please be sure that anything added or modified in this function that can
     * be removed during uninstall should be removed with hook_uninstall().
     *
     * @see hook_uninstall()
     * @see hook_schema()
     */
    function hook_install() {
      // Populate the default {node_access} record.
      db_insert('node_access')
        ->fields(array(
          'nid' => 0,
          'gid' => 0,
          'realm' => 'all',
          'grant_view' => 1,
          'grant_update' => 0,
          'grant_delete' => 0,
        ))
        ->execute();
    }
    
    /**
     * Perform a single update.
     *
     * For each patch which requires a database change add a new hook_update_N()
     * which will be called by update.php. The database updates are numbered 
     * sequentially according to the version of Drupal you are compatible with.
     *
     * Schema updates should adhere to the Schema API:
     * @link http://drupal.org/node/150215 http://drupal.org/node/150215 @endlink
     *
     * Database updates consist of 3 parts:
     * - 1 digit for Drupal core compatibility
     * - 1 digit for your module's major release version (e.g. is this the 5.x-1.* (1) or 5.x-2.* (2) series of your module?)
     * - 2 digits for sequential counting starting with 00
     *
     * The 2nd digit should be 0 for initial porting of your module to a new Drupal
     * core API.
     *
     * Examples:
     * - mymodule_update_5200()
     *   - This is the first update to get the database ready to run mymodule 5.x-2.*.
     * - mymodule_update_6000()
     *   - This is the required update for mymodule to run with Drupal core API 6.x.
     * - mymodule_update_6100()
     *   - This is the first update to get the database ready to run mymodule 6.x-1.*.
     * - mymodule_update_6200()
     *   - This is the first update to get the database ready to run mymodule 6.x-2.*.
     *     Users can directly update from 5.x-2.* to 6.x-2.* and they get all 60XX
     *     and 62XX updates, but not 61XX updates, because those reside in the
     *     6.x-1.x branch only.
     *
     * A good rule of thumb is to remove updates older than two major releases of
     * Drupal. See hook_update_last_removed() to notify Drupal about the removals.
     *
     * Never renumber update functions.
     *
     * Further information about releases and release numbers:
     * - @link http://drupal.org/handbook/version-info http://drupal.org/handbook/version-info @endlink
     * - @link http://drupal.org/node/93999 http://drupal.org/node/93999 @endlink (Overview of contributions branches and tags)
     * - @link http://drupal.org/handbook/cvs/releases http://drupal.org/handbook/cvs/releases @endlink
     *
     * Implementations of this hook should be placed in a mymodule.install file in
     * the same directory as mymodule.module. Drupal core's updates are implemented
     * using the system module as a name and stored in database/updates.inc.
     *
     * If your update task is potentially time-consuming, you'll need to implement a
     * multipass update to avoid PHP timeouts. Multipass updates use the $sandbox
     * parameter provided by the batch API (normally, $context['sandbox']) to store
     * information between successive calls, and the $sandbox['#finished'] value
     * to provide feedback regarding completion level.
     *
     * See the batch operations page for more information on how to use the batch API:
     * @link http://drupal.org/node/146843 http://drupal.org/node/146843 @endlink
     *
     * @throws DrupalUpdateException, PDOException
     *   In case of error, update hooks should throw an instance of DrupalUpdateException
     *   with a meaningful message for the user. If a database query fails for whatever
     *   reason, it will throw a PDOException.
     *
     * @return
     *   Optionally update hooks may return a translated string that will be displayed
     *   to the user. If no message is returned, no message will be presented to the
     *   user.
     */
    function hook_update_N(&$sandbox) {
      // For non-multipass updates, the signature can simply be;
      // function hook_update_N() {
    
      // For most updates, the following is sufficient.
      db_add_field('mytable1', 'newcol', array('type' => 'int', 'not null' => TRUE, 'description' => 'My new integer column.'));
    
      // However, for more complex operations that may take a long time,
      // you may hook into Batch API as in the following example.
    
      // Update 3 users at a time to have an exclamation point after their names.
      // (They're really happy that we can do batch API in this hook!)
      if (!isset($sandbox['progress'])) {
        $sandbox['progress'] = 0;
        $sandbox['current_uid'] = 0;
        // We'll -1 to disregard the uid 0...
        $sandbox['max'] = db_query('SELECT COUNT(DISTINCT uid) FROM {users}')->fetchField() - 1;
      }
      db_select('users', 'u')
        ->fields('u', array('uid', 'name'))
        ->condition('uid', $sandbox['current_uid'], '>')
        ->range(0, 3)
        ->orderBy('uid', 'ASC')
        ->execute();
      foreach ($users as $user) {
        $user->name .= '!';
        db_update('users')
          ->fields(array('name' => $user->name))
          ->condition('uid', $user->uid)
          ->execute();
    
        $sandbox['progress']++;
        $sandbox['current_uid'] = $user->uid;
      }
    
      $sandbox['#finished'] = empty($sandbox['max']) ? 1 : ($sandbox['progress'] / $sandbox['max']);
    
      // To display a message to the user when the update is completed, return it.
      // If you do not want to display a completion message, simply return nothing.
      return t('The update did what it was supposed to do.');
    
      // In case of an error, simply throw an exception with an error message.
      throw new DrupalUpdateException('Something went wrong; here is what you should do.');
    }
    
    /**
     * Return an array of information about module update dependencies.
     *
     * This can be used to indicate update functions from other modules that your
     * module's update functions depend on, or vice versa. It is used by the update
     * system to determine the appropriate order in which updates should be run, as
     * well as to search for missing dependencies.
     *
     * Implementations of this hook should be placed in a mymodule.install file in
     * the same directory as mymodule.module.
     *
     * @return
     *   A multidimensional array containing information about the module update
     *   dependencies. The first two levels of keys represent the module and update
     *   number (respectively) for which information is being returned, and the
     *   value is an array of information about that update's dependencies. Within
     *   this array, each key represents a module, and each value represents the
     *   number of an update function within that module. In the event that your
     *   update function depends on more than one update from a particular module,
     *   you should always list the highest numbered one here (since updates within
     *   a given module always run in numerical order).
     *
     * @see update_resolve_dependencies()
     * @see hook_update_N()
     */
    function hook_update_dependencies() {
      // Indicate that the mymodule_update_7000() function provided by this module
      // must run after the another_module_update_7002() function provided by the
      // 'another_module' module.
      $dependencies['mymodule'][7000] = array(
        'another_module' => 7002,
      );
      // Indicate that the mymodule_update_7001() function provided by this module
      // must run before the yet_another_module_update_7004() function provided by
      // the 'yet_another_module' module. (Note that declaring dependencies in this
      // direction should be done only in rare situations, since it can lead to the
      // following problem: If a site has already run the yet_another_module
      // module's database updates before it updates its codebase to pick up the
      // newest mymodule code, then the dependency declared here will be ignored.)
      $dependencies['yet_another_module'][7004] = array(
        'mymodule' => 7001,
      );
      return $dependencies;
    }
    
    /**
     * Return a number which is no longer available as hook_update_N().
     *
     * If you remove some update functions from your mymodule.install file, you
     * should notify Drupal of those missing functions. This way, Drupal can
     * ensure that no update is accidentally skipped.
     *
     * Implementations of this hook should be placed in a mymodule.install file in
     * the same directory as mymodule.module.
     *
     * @return
     *   An integer, corresponding to hook_update_N() which has been removed from
     *   mymodule.install.
     *
     * @see hook_update_N()
     */
    function hook_update_last_removed() {
      // We've removed the 5.x-1.x version of mymodule, including database updates.
      // The next update function is mymodule_update_5200().
      return 5103;
    }
    
    /**
     * Remove any information that the module sets.
     *
     * The information that the module should remove includes:
     * - variables that the module has set using variable_set() or system_settings_form()
     * - modifications to existing tables
     *
     * The module should not remove its entry from the {system} table. Database tables
     * defined by hook_schema() will be removed automatically.
     *
     * The uninstall hook will fire when the module gets uninstalled but before the
     * module's database tables are removed, allowing your module to query its own
     * tables during this routine.
     *
     * @see hook_install()
     * @see hook_schema()
     */
    function hook_uninstall() {
      variable_del('upload_file_types');
    }
    
    /**
     * Perform necessary actions after module is enabled.
     *
     * The hook is called everytime module is enabled.
     */
    function hook_enable() {
      mymodule_cache_rebuild();
    }
    
    /**
     * Perform necessary actions before module is disabled.
     *
     * The hook is called everytime module is disabled.
     */
    function hook_disable() {
      mymodule_cache_rebuild();
    }
    
    /**
     * Perform necessary alterations to the list of files parsed by the registry.
     *
     * Modules can manually modify the list of files before the registry parses
     * them. The $modules array provides the .info file information, which includes
     * the list of files registered to each module. Any files in the list can then
     * be added to the list of files that the registry will parse, or modify
     * attributes of a file.
     *
     * A necessary alteration made by the core SimpleTest module is to force .test
     * files provided by disabled modules into the list of files parsed by the
     * registry.
     *
     * @param $files
     *   List of files to be parsed by the registry. The list will contain
     *   files found in each enabled module's info file and the core includes
     *   directory. The array is keyed by the file path and contains an array of
     *   the related module's name and weight as used internally by
     *   _registry_update() and related functions.
     *
     *   For example:
     *   @code
     *     $files["modules/system/system.module"] = array(
     *       'module' => 'system',
     *       'weight' => 0,
     *     );
     *   @endcode
     * @param $modules
     *   An array containing all module information stored in the {system} table.
     *   Each element of the array also contains the module's .info file
     *   information in the property 'info'. An additional 'dir' property has been
     *   added to the module information which provides the path to the directory
     *   in which the module resides. The example shows how to take advantage of
     *   both properties.
     *
     * @see _registry_update()
     * @see simpletest_test_get_all()
     */
    function hook_registry_files_alter(&$files, $modules) {
      foreach ($modules as $module) {
        // Only add test files for disabled modules, as enabled modules should
        // already include any test files they provide.
        if (!$module->status) {
          $dir = $module->dir;
          foreach ($module->info['files'] as $file) {
            if (substr($file, -5) == '.test') {
              $files["$dir/$file"] = array('module' => $module->name, 'weight' => $module->weight);
            }
          }
        }
      }
    }
    
    /**
     * Return an array of tasks to be performed by an installation profile.
     *
     * Any tasks you define here will be run, in order, after the installer has
     * finished the site configuration step but before it has moved on to the
     * final import of languages and the end of the installation. You can have any
     * number of custom tasks to perform during this phase.
     *
     * Each task you define here corresponds to a callback function which you must
     * separately define and which is called when your task is run. This function
     * will receive the global installation state variable, $install_state, as
     * input, and has the opportunity to access or modify any of its settings. See
     * the install_state_defaults() function in the installer for the list of
     * $install_state settings used by Drupal core.
     *
     * At the end of your task function, you can indicate that you want the
     * installer to pause and display a page to the user by returning any themed
     * output that should be displayed on that page (but see below for tasks that
     * use the form API or batch API; the return values of these task functions are
     * handled differently). You should also use drupal_set_title() within the task
     * callback function to set a custom page title. For some tasks, however, you
     * may want to simply do some processing and pass control to the next task
     * without ending the page request; to indicate this, simply do not send back
     * a return value from your task function at all. This can be used, for
     * example, by installation profiles that need to configure certain site
     * settings in the database without obtaining any input from the user.
     *
     * The task function is treated specially if it defines a form or requires
     * batch processing; in that case, you should return either the form API
     * definition or batch API array, as appropriate. See below for more
     * information on the 'type' key that you must define in the task definition
     * to inform the installer that your task falls into one of those two
     * categories. It is important to use these APIs directly, since the installer
     * may be run non-interactively (for example, via a command line script), all
     * in one page request; in that case, the installer will automatically take
     * care of submitting forms and processing batches correctly for both types of
     * installations. You can inspect the $install_state['interactive'] boolean to
     * see whether or not the current installation is interactive, if you need
     * access to this information.
     *
     * Remember that a user installing Drupal interactively will be able to reload
     * an installation page multiple times, so you should use variable_set() and
     * variable_get() if you are collecting any data that you need to store and
     * inspect later. It is important to remove any temporary variables using
     * variable_del() before your last task has completed and control is handed
     * back to the installer.
     *
     * @return
     *   A keyed array of tasks the profile will perform during the final stage of
     *   the installation. Each key represents the name of a function (usually a
     *   function defined by this profile, although that is not strictly required)
     *   that is called when that task is run. The values are associative arrays
     *   containing the following key-value pairs (all of which are optional):
     *     - 'display_name'
     *       The human-readable name of the task. This will be displayed to the
     *       user while the installer is running, along with a list of other tasks
     *       that are being run. Leave this unset to prevent the task from
     *       appearing in the list.
     *     - 'display'
     *       This is a boolean which can be used to provide finer-grained control
     *       over whether or not the task will display. This is mostly useful for
     *       tasks that are intended to display only under certain conditions; for
     *       these tasks, you can set 'display_name' to the name that you want to
     *       display, but then use this boolean to hide the task only when certain
     *       conditions apply.
     *     - 'type'
     *       A string representing the type of task. This parameter has three
     *       possible values:
     *       - 'normal': This indicates that the task will be treated as a regular
     *       callback function, which does its processing and optionally returns
     *       HTML output. This is the default behavior which is used when 'type' is
     *       not set.
     *       - 'batch': This indicates that the task function will return a batch
     *       API definition suitable for batch_set(). The installer will then take
     *       care of automatically running the task via batch processing.
     *       - 'form': This indicates that the task function will return a standard
     *       form API definition (and separately define validation and submit
     *       handlers, as appropriate). The installer will then take care of
     *       automatically directing the user through the form submission process.
     *     - 'run'
     *       A constant representing the manner in which the task will be run. This
     *       parameter has three possible values:
     *       - INSTALL_TASK_RUN_IF_NOT_COMPLETED: This indicates that the task will
     *       run once during the installation of the profile. This is the default
     *       behavior which is used when 'run' is not set.
     *       - INSTALL_TASK_SKIP: This indicates that the task will not run during
     *       the current installation page request. It can be used to skip running
     *       an installation task when certain conditions are met, even though the
     *       task may still show on the list of installation tasks presented to the
     *       user.
     *       - INSTALL_TASK_RUN_IF_REACHED: This indicates that the task will run
     *       on each installation page request that reaches it. This is rarely
     *       necessary for an installation profile to use; it is primarily used by
     *       the Drupal installer for bootstrap-related tasks.
     *     - 'function'
     *       Normally this does not need to be set, but it can be used to force the
     *       installer to call a different function when the task is run (rather
     *       than the function whose name is given by the array key). This could be
     *       used, for example, to allow the same function to be called by two
     *       different tasks.
     *
     * @see install_state_defaults()
     * @see batch_set()
     */
    function hook_install_tasks() {
      // Here, we define a variable to allow tasks to indicate that a particular,
      // processor-intensive batch process needs to be triggered later on in the
      // installation.
      $myprofile_needs_batch_processing = variable_get('myprofile_needs_batch_processing', FALSE);
      $tasks = array(
        // This is an example of a task that defines a form which the user who is
        // installing the site will be asked to fill out. To implement this task,
        // your profile would define a function named myprofile_data_import_form()
        // as a normal form API callback function, with associated validation and
        // submit handlers. In the submit handler, in addition to saving whatever
        // other data you have collected from the user, you might also call
        // variable_set('myprofile_needs_batch_processing', TRUE) if the user has
        // entered data which requires that batch processing will need to occur
        // later on.
        'myprofile_data_import_form' => array(
          'display_name' => st('Data import options'),
          'type' => 'form',
        ),
        // Similarly, to implement this task, your profile would define a function
        // named myprofile_settings_form() with associated validation and submit
        // handlers. This form might be used to collect and save additional
        // information from the user that your profile needs. There are no extra
        // steps required for your profile to act as an "installation wizard"; you
        // can simply define as many tasks of type 'form' as you wish to execute,
        // and the forms will be presented to the user, one after another.
        'myprofile_settings_form' => array(
          'display_name' => st('Additional options'),
          'type' => 'form',
        ),
        // This is an example of a task that performs batch operations. To
        // implement this task, your profile would define a function named
        // myprofile_batch_processing() which returns a batch API array definition
        // that the installer will use to execute your batch operations. Due to the
        // 'myprofile_needs_batch_processing' variable used here, this task will be
        // hidden and skipped unless your profile set it to TRUE in one of the
        // previous tasks.
        'myprofile_batch_processing' => array(
          'display_name' => st('Import additional data'),
          'display' => $myprofile_needs_batch_processing,
          'type' => 'batch',
          'run' => $myprofile_needs_batch_processing ? INSTALL_TASK_RUN_IF_NOT_COMPLETED : INSTALL_TASK_SKIP,
        ),
        // This is an example of a task that will not be displayed in the list that
        // the user sees. To implement this task, your profile would define a
        // function named myprofile_final_site_setup(), in which additional,
        // automated site setup operations would be performed. Since this is the
        // last task defined by your profile, you should also use this function to
        // call variable_del('myprofile_needs_batch_processing') and clean up the
        // variable that was used above. If you want the user to pass to the final
        // Drupal installation tasks uninterrupted, return no output from this
        // function. Otherwise, return themed output that the user will see (for
        // example, a confirmation page explaining that your profile's tasks are
        // complete, with a link to reload the current page and therefore pass on
        // to the final Drupal installation tasks when the user is ready to do so).
        'myprofile_final_site_setup' => array(
        ),
      );
      return $tasks;
    }
    
    /**
     * Change the page the user is sent to by drupal_goto().
     *
     * @param &$path
     *   A Drupal path or a full URL.
     * @param &$options
     *   An associative array of additional URL options to pass to url().
     * @param &$http_response_code
     *   The HTTP status code to use for the redirection. See drupal_goto() for more
     *   information.
     */
    function hook_drupal_goto_alter(&$path, &$options, &$http_response_code) {
      // A good addition to misery module.
      $http_response_code = 500;
    }
    
    /**
     * Alter XHTML HEAD tags before they are rendered by drupal_get_html_head().
     *
     * Elements available to be altered are only those added using
     * drupal_add_html_head_link() or drupal_add_html_head(). CSS and JS files
     * are handled using drupal_add_css() and drupal_add_js(), so the head links
     * for those files will not appear in the $head_elements array.
     *
     * @param $head_elements
     *   An array of renderable elements. Generally the values of the #attributes
     *   array will be the most likely target for changes.
     */
    function hook_html_head_alter(&$head_elements) {
      foreach($head_elements as $key => $element) {
        if (isset($element['#attributes']['rel']) && $element['#attributes']['rel'] == 'canonical') {
          // I want a custom canonical url.
          $head_elements[$key]['#attributes']['href'] = mymodule_canonical_url();
        }
      }
    }
    
    /**
     * Alter the full list of installation tasks.
     *
     * @param $tasks
     *   An array of all available installation tasks, including those provided by
     *   Drupal core. You can modify this array to change or replace any part of
     *   the Drupal installation process that occurs after the installation profile
     *   is selected.
     * @param $install_state
     *   An array of information about the current installation state.
     */
    function hook_install_tasks_alter(&$tasks, $install_state) {
      // Replace the "Choose language" installation task provided by Drupal core
      // with a custom callback function defined by this installation profile.
      $tasks['install_select_locale']['function'] = 'myprofile_locale_selection';
    }
    
    /**
     * Alter MIME type mappings used to determine MIME type from a file extension.
     *
     * This hook is run when file_mimetype_mapping() is called. It is used to
     * allow modules to add to or modify the default mapping from
     * file_default_mimetype_mapping().
     *
     * @param $mapping
     *   An array of mimetypes correlated to the extensions that relate to them.
     *   The array has 'mimetypes' and 'extensions' elements, each of which is an
     *   array.
     * @see file_default_mimetype_mapping()
     */
    function hook_file_mimetype_mapping_alter(&$mapping) {
      // Add new MIME type 'drupal/info'.
      $mapping['mimetypes']['example_info'] = 'drupal/info';
      // Add new extension '.info' and map it to the 'drupal/info' MIME type.
      $mapping['extensions']['info'] = 'example_info';
      // Override existing extension mapping for '.ogg' files.
      $mapping['extensions']['ogg'] = 189;
    }
    
    /**
     * Declares information about actions.
     *
     * Any module can define actions, and then call actions_do() to make those
     * actions happen in response to events. The trigger module provides a user
     * interface for associating actions with module-defined triggers, and it makes
     * sure the core triggers fire off actions when their events happen.
     *
     * An action consists of two or three parts:
     * - an action definition (returned by this hook)
     * - a function which performs the action (which by convention is named
     *   MODULE_description-of-function_action)
     * - an optional form definition function that defines a configuration form
     *   (which has the name of the action function with '_form' appended to it.)
     *
     * The action function takes two to four arguments, which come from the input
     * arguments to actions_do().
     *
     * @return
     *   An associative array of action descriptions. The keys of the array
     *   are the names of the action functions, and each corresponding value
     *   is an associative array with the following key-value pairs:
     *   - 'type': The type of object this action acts upon. Core actions have types
     *     'node', 'user', 'comment', and 'system'.
     *   - 'label': The human-readable name of the action, which should be passed
     *     through the t() function for translation.
     *   - 'configurable': If FALSE, then the action doesn't require any extra
     *     configuration. If TRUE, then your module must define a form function with
     *     the same name as the action function with '_form' appended (e.g., the
     *     form for 'node_assign_owner_action' is 'node_assign_owner_action_form'.)
     *     This function takes $context as its only parameter, and is paired with
     *     the usual _submit function, and possibly a _validate function.
     *   - 'triggers': An array of the events (that is, hooks) that can trigger this
     *     action. For example: array('node_insert', 'user_update'). You can also
     *     declare support for any trigger by returning array('any') for this value.
     *   - 'behavior': (optional) A machine-readable array of behaviors of this
     *     action, used to signal additionally required actions that may need to be
     *     triggered. Currently recognized behaviors by Trigger module:
     *     - 'changes_property': If an action with this behavior is assigned to a
     *       trigger other than a "presave" hook, any save actions also assigned to
     *       this trigger are moved later in the list. If no save action is present,
     *       one will be added.
     *       Modules that are processing actions (like Trigger module) should take
     *       special care for the "presave" hook, in which case a dependent "save"
     *       action should NOT be invoked.
     *
     * @ingroup actions
     */
    function hook_action_info() {
      return array(
        'comment_unpublish_action' => array(
          'type' => 'comment',
          'label' => t('Unpublish comment'),
          'configurable' => FALSE,
          'behavior' => array('changes_property'),
          'triggers' => array('comment_presave', 'comment_insert', 'comment_update'),
        ),
        'comment_unpublish_by_keyword_action' => array(
          'type' => 'comment',
          'label' => t('Unpublish comment containing keyword(s)'),
          'configurable' => TRUE,
          'behavior' => array('changes_property'),
          'triggers' => array('comment_presave', 'comment_insert', 'comment_update'),
        ),
        'comment_save_action' => array(
          'type' => 'comment',
          'label' => t('Save comment'),
          'configurable' => FALSE,
          'triggers' => array('comment_insert', 'comment_update'),
        ),
      );
    }
    
    /**
     * Executes code after an action is deleted.
     *
     * @param $aid
     *   The action ID.
     */
    function hook_actions_delete($aid) {
      db_delete('actions_assignments')
        ->condition('aid', $aid)
        ->execute();
    }
    
    /**
     * Alters the actions declared by another module.
     *
     * Called by actions_list() to allow modules to alter the return values from
     * implementations of hook_action_info().
     *
     * @see trigger_example_action_info_alter().
     */
    function hook_action_info_alter(&$actions) {
      $actions['node_unpublish_action']['label'] = t('Unpublish and remove from public view.');
    }
    
    /**
     * Declare archivers to the system.
     *
     * An archiver is a class that is able to package and unpackage one or more files
     * into a single possibly compressed file.  Common examples of such files are
     * zip files and tar.gz files.  All archiver classes must implement
     * ArchiverInterface.
     *
     * Each entry should be keyed on a unique value, and specify three
     * additional keys:
     * - class: The name of the PHP class for this archiver.
     * - extensions: An array of file extensions that this archiver supports.
     * - weight: This optional key specifies the weight of this archiver.
     *   When mapping file extensions to archivers, the first archiver by
     *   weight found that supports the requested extension will be used.
     *
     * @see hook_archiver_info_alter()
     */
    function hook_archiver_info() {
      return array(
        'tar' => array(
          'class' => 'ArchiverTar',
          'extensions' => array('tar', 'tar.gz', 'tar.bz2'),
        ),
      );
    }
    
    /**
     * Alter archiver information declared by other modules.
     *
     * See hook_archiver_info() for a description of archivers and the archiver
     * information structure.
     *
     * @param $info
     *   Archiver information to alter (return values from hook_archiver_info()).
     */
    function hook_archiver_info_alter(&$info) {
      $info['tar']['extensions'][] = 'tgz';
    }
    
    /**
     * Defines additional date types.
     *
     * Next to the 'long', 'medium' and 'short' date types defined in core, any
     * module can define additional types that can be used when displaying dates. A
     * date type is a key which can be passed to format_date() to return a date in
     * the configured display format.
     *
     * To avoid namespace collisions with date types defined by other modules, it is
     * recommended that each date type starts with the module name. A date type
     * can consist of letters, numbers and underscores.
     *
     * @see hook_date_formats()
     * @see format_date()
     *
     * @return
     *   A list of date types in 'key' => 'label' format.
     */
    function hook_date_format_types() {
      return array(
        'long' => t('Long'),
        'medium' => t('Medium'),
        'short' => t('Short'),
      );
    }
    
    /**
     * Defines additional date formats.
     *
     * Next to the 'long', 'medium' and 'short' date types defined in core, any
     * module can define additional types that can be used when displaying dates. A
     * date type is a key which can be passed to format_date() to return a date in
     * the configured displayed format. A date format is a string defining the date
     * and time elements to use. For example, a date type could be
     * 'mymodule_extra_long', while a date format is like 'Y-m-d'.
     *
     * New date types must first be declared using hook_date_format_types(). It is
     * then possible to define one or more date formats for each.
     *
     * A module may also extend the list date formats defined for a date type
     * provided by another module.
     *
     * There may be more than one format for the same locale. For example d/m/Y and
     * Y/m/d work equally well in some locales. It may also be necessary to define
     * multiple versions of the same date format, for example, one using AM, one
     * with PM and one without the time at all.
     *
     * However at the same time you may wish to define some additional date formats
     * that aren't specific to any one locale, for example, "Y m". For these cases
     * the locales field should be omitted.
     *
     * @see hook_date_format_types()
     *
     * @return
     *   A list of date formats. Each date format is a keyed array
     *   consisting of three elements:
     *   - 'type': the date type is a key used to identify which date format to
     *     display. It consists of letters, numbers and underscores, e.g. 'long',
     *     'short', 'mymodule_extra_long'. It must first be declared in
     *     hook_date_format_types() unless extending a type provided by another
     *     module.
     *   - 'format': a string defining the date and time elements to use. It
     *     can contain any of the formatting options described at
     *     http://php.net/manual/en/function.date.php
     *   - 'locales': (optional) an array of 2 and 5 character language codes, for
     *     example, 'en', 'en-us'. The language codes are used to determine which
     *     date format to display for the user's current language. If more than one
     *     date format is suggested for the same date type and locale, then the
     *     first one will be used unless overridden via
     *     admin/config/regional/date-time/locale. If your date format is not
     *     language specific, leave this field empty.
     */
    function hook_date_formats() {
      return array(
        array(
          'type' => 'mymodule_extra_long',
          'format' => 'l jS F Y H:i:s e',
          'locales' => array('en-ie'),
        ),
        array(
          'type' => 'mymodule_extra_long',
          'format' => 'l jS F Y h:i:sa',
          'locales' => array('en', 'en-us'),
        ),
        array(
          'type' => 'short',
          'format' => 'F Y',
          'locales' => array(),
        ),
      );
    }
    
    /**
     * Alters date types and formats declared by another module.
     *
     * Called by _system_date_format_types_build() to allow modules to alter the
     * return values from implementations of hook_date_formats().
     */
    function hook_date_formats_alter(&$formats) {
      foreach ($formats as $id => $format) {
        $formats[$id]['locales'][] = 'en-ca';
      }
    }
    
    /**
     * Alters the router item for the active menu handler.
     *
     * Called by menu_execute_active_handler() to allow modules to alter the
     * information that will be used to handle the page request. Only use this
     * hook if an alteration specific to the page request is needed. Otherwise
     * use hook_menu_alter().
     *
     * @param $router_item
     *   An array with the following keys:
     *   - access: Boolean. Whether the user is allowed to see this page.
     *   - file: A path to a file to include prior to invoking the page callback.
     *   - page_callback: The function to call to build the page content.
     *   - page_arguments: Arguments to pass to the page callback.
     *   - delivery_callback: The function to call to deliver the result of the
     *     page callback to the browser.
     * @param $path
     *   The drupal path that was used for retrieving the router item.
     *
     * @see menu_execute_active_handler()
     * @see hook_menu()
     * @see hook_menu_alter()
     */
    function hook_menu_active_handler_alter(&$router_item, $path = NULL) {
      // Turn off access for all pages for all users.
      $router_item['access'] = FALSE;
    }
    
    /**
     * Alters the delivery callback used to send the result of the page callback to the browser.
     *
     * Called by drupal_deliver_page() to allow modules to alter how the
     * page is delivered to the browser.
     *
     * This hook is intended for altering the delivery callback based on
     * information unrelated to the path of the page accessed. For example,
     * it can be used to set the delivery callback based on a HTTP request
     * header (as shown in the code sample). To specify a delivery callback
     * based on path information, use hook_menu(), hook_menu_alter() or
     * hook_menu_active_handler_alter().
     *
     * This hook can also be used as an API function that can be used to explicitly
     * set the delivery callback from some other function. For example, for a module
     * named MODULE:
     * @code
     * function MODULE_page_delivery_callback_alter(&$callback, $set = FALSE) {
     *   static $stored_callback;
     *   if ($set) {
     *     $stored_callback = $callback;
     *   }
     *   elseif (isset($stored_callback)) {
     *     $callback = $stored_callback;
     *   }
     * }
     * function SOMEWHERE_ELSE() {
     *   $desired_delivery_callback = 'foo';
     *   MODULE_page_delivery_callback_alter($desired_delivery_callback, TRUE);
     * }
     * @endcode
     *
     * @param $callback
     *   The name of a function.
     *
     * @see drupal_deliver_page()
     */
    function hook_page_delivery_callback_alter(&$callback) {
      // jQuery sets a HTTP_X_REQUESTED_WITH header of 'XMLHttpRequest'.
      // If a page would normally be delivered as an html page, and it is called
      // from jQuery, deliver it instead as an AJAX response.
      if (isset($_SERVER['HTTP_X_REQUESTED_WITH']) && $_SERVER['HTTP_X_REQUESTED_WITH'] == 'XMLHttpRequest' && $callback == 'drupal_deliver_html_page') {
        $callback = 'ajax_deliver';
      }
    }
    
    /**
     * Alters theme operation links.
     *
     * @param $theme_groups
     *   An associative array containing groups of themes.
     *
     * @see system_themes_page()
     */
    function hook_system_themes_page_alter(&$theme_groups) {
      foreach ($theme_groups as $state => &$group) {
        foreach($theme_groups[$state] as &$theme) {
          // Add a foo link to each list of theme operations.
          $theme->operations[] = l(t('Foo'), 'admin/appearance/foo', array('query' => array('theme' => $theme->name)));
        }
      }
    }
    
    /**
     * Alters inbound URL requests.
     *
     * @param $path
     *   The path being constructed, which, if a path alias, has been resolved to a
     *   Drupal path by the database, and which also may have been altered by other
     *   modules before this one.
     * @param $original_path
     *   The original path, before being checked for path aliases or altered by any
     *   modules.
     * @param $path_language
     *   The language of the path.
     *
     * @see drupal_get_normal_path()
     */
    function hook_url_inbound_alter(&$path, $original_path, $path_language) {
      // Create the path user/me/edit, which allows a user to edit their account.
      if (preg_match('|^user/me/edit(/.*)?|', $path, $matches)) {
        global $user;
        $path = 'user/' . $user->uid . '/edit' . $matches[1];
      }
    }
    
    /**
     * Alters outbound URLs.
     *
     * @param $path
     *   The outbound path to alter, not adjusted for path aliases yet. It won't be
     *   adjusted for path aliases until all modules are finished altering it, thus
     *   being consistent with hook_url_alter_inbound(), which adjusts for all path
     *   aliases before allowing modules to alter it. This may have been altered by
     *   other modules before this one.
     * @param $options
     *   A set of URL options for the URL so elements such as a fragment or a query
     *   string can be added to the URL.
     * @param $original_path
     *   The original path, before being altered by any modules.
     *
     * @see url()
     */
    function hook_url_outbound_alter(&$path, &$options, $original_path) {
      // Use an external RSS feed rather than the Drupal one.
      if ($path == 'rss.xml') {
        $path = 'http://example.com/rss.xml';
        $options['external'] = TRUE;
      }
    
      // Instead of pointing to user/[uid]/edit, point to user/me/edit.
      if (preg_match('|^user/([0-9]*)/edit(/.*)?|', $path, $matches)) {
        global $user;
        if ($user->uid == $matches[1]) {
          $path = 'user/me/edit' . $matches[2];
        }
      }
    }
    
    /**
     * Alter the username that is displayed for a user.
     *
     * Called by format_username() to allow modules to alter the username that's
     * displayed. Can be used to ensure user privacy in situations where
     * $account->name is too revealing.
     *
     * @param &$name
     *   The string that format_username() will return.
     *
     * @param $account
     *   The account object passed to format_username().
     *
     * @see format_username()
     */
    function hook_username_alter(&$name, $account) {
      // Display the user's uid instead of name.
      if (isset($account->uid)) {
        $name = t('User !uid', array('!uid' => $account->uid));
      }
    }
    
    /**
     * Provide replacement values for placeholder tokens.
     *
     * @param $type
     *   The type of token being replaced. 'node', 'user', and 'date' are common.
     * @param $tokens
     *   An array of tokens to be replaced, keyed by the literal text of the token
     *   as it appeared in the source text.
     * @param $data
     *   (optional) An associative array of objects to be used when generating replacement
     *   values.
     * @param $options
     *   (optional) A associative array of options to control the token
     *   replacement process. Common options are:
     *   - 'language' A language object to be used when generating locale-sensitive
     *     tokens.
     *   - 'sanitize' A boolean flag indicating that tokens should be sanitized for
     *     display to a web browser.
     *
     * @return
     *   An associative array of replacement values, keyed by the original 'raw'
     *   tokens that were found in the source text. For example:
     *   $results['[node:title]'] = 'My new node';
     */
    function hook_tokens($type, $tokens, array $data = array(), array $options = array()) {
      $url_options = array('absolute' => TRUE);
      if (isset($options['language'])) {
        $url_options['language'] = $options['language'];
        $language_code = $options['language']->language;
      }
      else {
        $language_code = NULL;
      }
      $sanitize = !empty($options['sanitize']);
    
      $replacements = array();
    
      if ($type == 'node' && !empty($data['node'])) {
        $node = $data['node'];
    
        foreach ($tokens as $name => $original) {
          switch ($name) {
            // Simple key values on the node.
            case 'nid':
              $replacements[$original] = $node->nid;
              break;
    
            case 'title':
              $replacements[$original] = $sanitize ? check_plain($node->title) : $node->title;
              break;
    
            case 'edit-url':
              $replacements[$original] = url('node/' . $node->nid . '/edit', $url_options);
              break;
    
            // Default values for the chained tokens handled below.
            case 'author':
              $name = ($node->uid == 0) ? variable_get('anonymous', t('Anonymous')) : $node->name;
              $replacements[$original] = $sanitize ? filter_xss($name) : $name;
              break;
    
            case 'created':
              $replacements[$original] = format_date($node->created, 'medium', '', NULL, $language_code);
              break;
          }
        }
    
        if ($author_tokens = token_find_with_prefix($tokens, 'author')) {
          $author = user_load($node->uid);
          $replacements += token_generate('user', $author_tokens, array('user' => $author), $options);
        }
    
        if ($created_tokens = token_find_with_prefix($tokens, 'created')) {
          $replacements += token_generate('date', $created_tokens, array('date' => $node->created), $options);
        }
      }
    
      return $replacements;
    }
    
    /**
     * Provide metadata about available placeholder tokens and token types.
     *
     * @return
     *   An associative array of available tokens and token types, each containing
     *   the raw name of the token or type, its user-friendly name, and a verbose
     *   description.
     *
     * @see hook_token_info_alter()
     */
    function hook_token_info() {
      $type = array(
        'name' => t('Nodes'),
        'description' => t('Tokens related to individual nodes.'),
        'needs-data' => 'node',
      );
    
      // Core tokens for nodes.
      $node['nid'] = array(
        'name' => t("Node ID"),
        'description' => t("The unique ID of the node."),
      );
      $node['title'] = array(
        'name' => t("Title"),
        'description' => t("The title of the node."),
      );
      $node['edit-url'] = array(
        'name' => t("Edit URL"),
        'description' => t("The URL of the node's edit page."),
      );
    
      // Chained tokens for nodes.
      $node['created'] = array(
        'name' => t("Date created"),
        'description' => t("The date the node was posted."),
        'type' => 'date',
      );
      $node['author'] = array(
        'name' => t("Author"),
        'description' => t("The author of the node."),
        'type' => 'user',
      );
    
      return array(
        'types' => array('node' => $type),
        'tokens' => array('node' => $node),
      );
    }
    
    /**
     * Alter the metadata about available placeholder tokens and token types.
     *
     * @param $data
     *   The associative array of token definitions from hook_token_info().
     *
     * @see hook_token_info()
     */
    function hook_token_info_alter(&$data) {
      // Modify description of node tokens for our site.
      $node['nid'] = array(
        'name' => t("Node ID"),
        'description' => t("The unique ID of the article."),
      );
      $node['title'] = array(
        'name' => t("Title"),
        'description' => t("The title of the article."),
      );
    
      // Chained tokens for nodes.
      $node['created'] = array(
        'name' => t("Date created"),
        'description' => t("The date the article was posted."),
        'type' => 'date',
      );
    }
    
    /**
     * Alter the default country list.
     *
     * @param $countries
     *   The associative array of countries keyed by ISO 3166-1 country code.
     *
     * @see country_get_list()
     * @see _country_get_predefined_list()
     */
    function hook_countries_alter(&$countries) {
      // Quebec has seceded from Canada. Add to country list.
      $countries['QC'] = 'Quebec';
    }
    /**
     * @} End of "addtogroup hooks".
     */