module.inc 31.2 KB
Newer Older
1 2 3
<?php
// $Id$

4 5 6 7 8
/**
 * @file
 * API for loading and interacting with Drupal modules.
 */

9
/**
10
 * Load all the modules that have been enabled in the system table.
11
 *
12 13 14 15 16 17
 * @param $bootstrap
 *   Whether to load only the reduced set of modules loaded in "bootstrap mode"
 *   for cached pages. See bootstrap.inc.
 * @return
 *   If $bootstrap is NULL, return a boolean indicating whether all modules
 *   have been loaded.
18
 */
19
function module_load_all($bootstrap = FALSE) {
20 21 22 23 24 25 26 27
  static $has_run = FALSE;

  if (isset($bootstrap)) {
    foreach (module_list(TRUE, $bootstrap) as $module) {
      drupal_load('module', $module);
    }
    // $has_run will be TRUE if $bootstrap is FALSE.
    $has_run = !$bootstrap;
28
  }
29
  return $has_run;
30 31
}

32

33
/**
34 35
 * Collect a list of all loaded modules. During the bootstrap, return only
 * vital modules. See bootstrap.inc
36 37 38 39
 *
 * @param $refresh
 *   Whether to force the module list to be regenerated (such as after the
 *   administrator has changed the system settings).
40 41 42
 * @param $bootstrap
 *   Whether to return the reduced set of modules loaded in "bootstrap mode"
 *   for cached pages. See bootstrap.inc.
43
 * @param $sort
44 45
 *   By default, modules are ordered by weight and module name. Set this option
 *   to TRUE to return a module list ordered only by module name.
46 47 48
 * @param $fixed_list
 *   (Optional) Override the module list with the given modules. Stays until the
 *   next call with $refresh = TRUE.
49 50 51 52
 * @return
 *   An associative array whose keys and values are the names of all loaded
 *   modules.
 */
53
function module_list($refresh = FALSE, $bootstrap = FALSE, $sort = FALSE, $fixed_list = NULL) {
54
  static $list = array(), $sorted_list;
55

56
  if (empty($list) || $refresh || $fixed_list) {
Dries's avatar
Dries committed
57
    $list = array();
58
    $sorted_list = NULL;
59 60 61 62 63
    if ($fixed_list) {
      foreach ($fixed_list as $name => $module) {
        drupal_get_filename('module', $name, $module['filename']);
        $list[$name] = $name;
      }
64 65
    }
    else {
66 67 68
      // As this is the $refresh case, make sure that system_list() returns
      // fresh data.
      drupal_static_reset('system_list');
69
      if ($bootstrap) {
70
        $list = system_list('bootstrap');
71 72
      }
      else {
73
        $list = system_list('module_enabled');
74
      }
75 76
    }
  }
77 78 79 80 81 82 83
  if ($sort) {
    if (!isset($sorted_list)) {
      $sorted_list = $list;
      ksort($sorted_list);
    }
    return $sorted_list;
  }
84 85 86
  return $list;
}

87 88 89 90
/**
 * Build a list of bootstrap modules and enabled modules and themes.
 *
 * @param $type
91 92 93 94
 *   The type of list to return:
 *   - module_enabled: All enabled modules.
 *   - bootstrap: All enabled modules required for bootstrap.
 *   - theme: All themes.
95 96
 *
 * @return
97 98 99
 *   An associative array of modules or themes, keyed by name, and having the
 *   respective database row as value. For $type 'module_enabled' and
 *   'bootstrap', the array values equal the keys.
100 101 102 103 104 105 106
 *
 * @see module_list()
 * @see list_themes()
 */
function system_list($type) {
  $lists = &drupal_static(__FUNCTION__);

107 108 109 110 111 112 113 114 115
  // For bootstrap modules, attempt to fetch the list from cache if possible.
  // if not fetch only the required information to fire bootstrap hooks
  // in case we are going to serve the page from cache.
  if ($type == 'bootstrap') {
    if ($cached = cache_get('bootstrap_modules', 'cache_bootstrap')) {
      $bootstrap_list = $cached->data;
    }
    else {
      $bootstrap_list = db_query("SELECT name, filename FROM {system} WHERE status = 1 AND bootstrap = 1 AND type = 'module' ORDER BY weight ASC, name ASC")->fetchAllAssoc('name');
116
      cache_set('bootstrap_modules', $bootstrap_list, 'cache_bootstrap');
117
    }
118
    // To avoid a separate database lookup for the filepath, prime the
119 120
    // drupal_get_filename() static cache for bootstrap modules only.
    // The rest is stored separately to keep the bootstrap module cache small.
121 122 123 124 125 126 127 128
    foreach ($bootstrap_list as $module) {
      drupal_get_filename('module', $module->name, $module->filename);
    }
    // We only return the module names here since module_list() doesn't need
    // the filename itself.
    $lists['bootstrap'] = array_keys($bootstrap_list);
  }
  // Otherwise build the list for enabled modules and themes.
129
  elseif (!isset($lists['module_enabled'])) {
130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157
    if ($cached = cache_get('system_list', 'cache_bootstrap')) {
      $lists = $cached->data;
    }
    else {
      $lists = array(
        'module_enabled' => array(),
        'theme' => array(),
        'filepaths' => array(),
      );
      // The module name (rather than the filename) is used as the fallback
      // weighting in order to guarantee consistent behavior across different
      // Drupal installations, which might have modules installed in different
      // locations in the file system. The ordering here must also be
      // consistent with the one used in module_implements().
      $result = db_query("SELECT * FROM {system} ORDER BY weight ASC, name ASC");
      foreach ($result as $record) {
        if ($record->type == 'module' && $record->status) {
          // Build a list of all enabled modules.
          $lists['module_enabled'][$record->name] = $record->name;
        }
        // Build a list of themes.
        if ($record->type == 'theme') {
          $lists['theme'][$record->name] = $record;
        }
        // Build a list of filenames so drupal_get_filename can use it.
        if ($record->status) {
          $lists['filepaths'][] = array('type' => $record->type, 'name' => $record->name, 'filepath' => $record->filename);
        }
158
      }
159 160
      cache_set('system_list', $lists, 'cache_bootstrap');
    }
161
    // To avoid a separate database lookup for the filepath, prime the
162 163 164
    // drupal_get_filename() static cache with all enabled modules and themes.
    foreach ($lists['filepaths'] as $item) {
      drupal_get_filename($item['type'], $item['name'], $item['filepath']);
165 166 167 168 169 170
    }
  }

  return $lists[$type];
}

171 172 173 174 175
/**
 * Reset all system_list() caches.
 */
function system_list_reset() {
  drupal_static_reset('system_list');
176
  drupal_static_reset('list_themes');
177
  cache_clear_all('bootstrap_modules', 'cache_bootstrap');
178
  cache_clear_all('system_list', 'cache_bootstrap');
179 180
}

181
/**
182
 * Find dependencies any level deep and fill in required by information too.
183 184 185
 *
 * @param $files
 *   The array of filesystem objects used to rebuild the cache.
186
 * @return
187 188 189 190 191
 *   The same array with the new keys for each module:
 *   - requires: An array with the keys being the modules that this module
 *     requires.
 *   - required_by: An array with the keys being the modules that will not work
 *     without this module.
192
 */
193
function _module_build_dependencies($files) {
194
  require_once DRUPAL_ROOT . '/includes/graph.inc';
195 196 197 198
  $roots = $files;
  foreach ($files as $filename => $file) {
    $graph[$file->name]['edges'] = array();
    if (isset($file->info['dependencies']) && is_array($file->info['dependencies'])) {
199 200 201 202
      foreach ($file->info['dependencies'] as $dependency) {
        $dependency_data = drupal_parse_dependency($dependency);
        $graph[$file->name]['edges'][$dependency_data['name']] = $dependency_data;
        unset($roots[$dependency_data['name']]);
203 204
      }
    }
205 206 207
  }
  drupal_depth_first_search($graph, array_keys($roots));
  foreach ($graph as $module => $data) {
208
    $files[$module]->required_by = isset($data['reverse_paths']) ? $data['reverse_paths'] : array();
209 210 211
    $files[$module]->requires = isset($data['paths']) ? $data['paths'] : array();
    $files[$module]->sort = $data['weight'];
  }
Steven Wittens's avatar
Steven Wittens committed
212 213 214
  return $files;
}

215 216 217 218 219 220 221 222
/**
 * Determine whether a given module exists.
 *
 * @param $module
 *   The name of the module (without the .module extension).
 * @return
 *   TRUE if the module is both installed and enabled.
 */
223
function module_exists($module) {
224
  $list = module_list();
225
  return isset($list[$module]);
226 227
}

Steven Wittens's avatar
Steven Wittens committed
228 229 230 231 232
/**
 * Load a module's installation hooks.
 */
function module_load_install($module) {
  // Make sure the installation API is available
233
  include_once DRUPAL_ROOT . '/includes/install.inc';
Steven Wittens's avatar
Steven Wittens committed
234

235
  module_load_include('install', $module);
236 237 238 239
}

/**
 * Load a module include file.
240
 *
241 242
 * Examples:
 * @code
243
 *   // Load node.admin.inc from the node module.
244
 *   module_load_include('inc', 'node', 'node.admin');
245
 *   // Load content_types.inc from the node module.
246
 *   module_load_include('inc', 'node', 'content_types');
247
 * @endcode
248
 *
249 250 251
 * Do not use this function to load an install file, use module_load_install()
 * instead. Do not use this function in a global context since it requires
 * Drupal to be fully bootstrapped, use require_once DRUPAL_ROOT . '/path/file'
252 253
 * instead.
 *
254 255 256 257 258
 * @param $type
 *   The include file's type (file extension).
 * @param $module
 *   The module to which the include file belongs.
 * @param $name
259
 *   Optionally, specify the base file name (without the $type extension).
260
 *   If not set, $module is used.
261 262 263 264 265 266
 */
function module_load_include($type, $module, $name = NULL) {
  if (empty($name)) {
    $name = $module;
  }

267
  if (function_exists('drupal_get_path')) {
268 269 270 271 272
    $file = DRUPAL_ROOT . '/' . drupal_get_path('module', $module) . "/$name.$type";
    if (is_file($file)) {
      require_once $file;
      return $file;
    }
273
  }
274
  return FALSE;
275 276 277 278 279 280 281 282 283 284
}

/**
 * Load an include file for each of the modules that have been enabled in
 * the system table.
 */
function module_load_all_includes($type, $name = NULL) {
  $modules = module_list();
  foreach ($modules as $module) {
    module_load_include($type, $module, $name);
Steven Wittens's avatar
Steven Wittens committed
285 286 287 288
  }
}

/**
289
 * Enable a given list of modules.
Steven Wittens's avatar
Steven Wittens committed
290
 *
291 292
 * @param $module_list
 *   An array of module names.
293 294 295 296
 * @param $enable_dependencies
 *   If TRUE, dependencies will automatically be added and enabled in the
 *   correct order. This incurs a significant performance cost, so use FALSE
 *   if you know $module_list is already complete and in the correct order.
297
 *
298 299
 * @return
 *   FALSE if one or more dependencies are missing, TRUE otherwise.
Steven Wittens's avatar
Steven Wittens committed
300
 */
301
function module_enable($module_list, $enable_dependencies = TRUE) {
302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338
  if ($enable_dependencies) {
    // Get all module data so we can find dependencies and sort.
    $module_data = system_rebuild_module_data();
    // Create an associative array with weights as values.
    $module_list = array_flip(array_values($module_list));

    while (list($module) = each($module_list)) {
      if (!isset($module_data[$module])) {
        // This module is not found in the filesystem, abort.
        return FALSE;
      }
      if ($module_data[$module]->status) {
        // Skip already enabled modules.
        unset($module_list[$module]);
        continue;
      }
      $module_list[$module] = $module_data[$module]->sort;

      // Add dependencies to the list, with a placeholder weight.
      // The new modules will be processed as the while loop continues.
      foreach ($module_data[$module]->info['dependencies'] as $dependency) {
        if (!isset($module_list[$dependency])) {
          $module_list[$dependency] = 0;
        }
      }
    }

    if (!$module_list) {
      // Nothing to do. All modules already enabled.
      return TRUE;
    }

    // Sort the module list by pre-calculated weights.
    arsort($module_list);
    $module_list = array_keys($module_list);
  }

339
  // Required for module installation checks.
340
  include_once DRUPAL_ROOT . '/includes/install.inc';
341 342 343

  $modules_installed = array();
  $modules_enabled = array();
344
  foreach ($module_list as $module) {
345
    // Only process modules that are not already enabled.
346 347 348 349
    $existing = db_query("SELECT status FROM {system} WHERE type = :type AND name = :name", array(
      ':type' => 'module',
      ':name' => $module))
      ->fetchObject();
350
    if ($existing->status == 0) {
351 352
      // Load the module's code.
      drupal_load('module', $module);
353
      module_load_install($module);
354 355 356 357 358

      // Update the database and module list to reflect the new module. This
      // needs to be done first so that the module's hook implementations,
      // hook_schema() in particular, can be called while it is being
      // installed.
359 360 361 362 363
      db_update('system')
        ->fields(array('status' => 1))
        ->condition('type', 'module')
        ->condition('name', $module)
        ->execute();
364 365 366 367 368 369 370 371 372
      // Refresh the module list to include it.
      system_list_reset();
      module_list(TRUE);
      module_implements('', FALSE, TRUE);
      _system_update_bootstrap_status();
      // Update the registry to include it.
      registry_update();
      // Refresh the schema to include it.
      drupal_get_schema(NULL, TRUE);
373 374
      // Clear entity cache.
      entity_info_cache_clear();
375 376 377 378 379 380

      // Now install the module if necessary.
      if (drupal_get_installed_schema_version($module, TRUE) == SCHEMA_UNINSTALLED) {
        drupal_install_schema($module);
        $versions = drupal_get_schema_versions($module);
        drupal_set_installed_schema_version($module, $versions ? max($versions) : SCHEMA_INSTALLED);
381 382
        // Allow the module to perform install tasks.
        module_invoke($module, 'install');
383 384
        // Record the fact that it was installed.
        $modules_installed[] = $module;
385
        watchdog('system', '%module module installed.', array('%module' => $module), WATCHDOG_INFO);
386
      }
387

388 389 390 391 392 393
      // Enable the module.
      module_invoke($module, 'enable');

      // Record the fact that it was enabled.
      $modules_enabled[] = $module;
      watchdog('system', '%module module enabled.', array('%module' => $module), WATCHDOG_INFO);
394
    }
395 396
  }

397
  // If any modules were newly installed, invoke hook_modules_installed().
398
  if (!empty($modules_installed)) {
399
    module_invoke_all('modules_installed', $modules_installed);
Steven Wittens's avatar
Steven Wittens committed
400
  }
401

402 403 404
  // If any modules were newly enabled, invoke hook_modules_enabled().
  if (!empty($modules_enabled)) {
    module_invoke_all('modules_enabled', $modules_enabled);
405
  }
406 407

  return TRUE;
Steven Wittens's avatar
Steven Wittens committed
408 409 410
}

/**
411
 * Disable a given set of modules.
Steven Wittens's avatar
Steven Wittens committed
412
 *
413 414
 * @param $module_list
 *   An array of module names.
415 416 417 418
 * @param $disable_dependents
 *   If TRUE, dependent modules will automatically be added and disabled in the
 *   correct order. This incurs a significant performance cost, so use FALSE
 *   if you know $module_list is already complete and in the correct order.
Steven Wittens's avatar
Steven Wittens committed
419
 */
420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448
function module_disable($module_list, $disable_dependents = TRUE) {
  if ($disable_dependents) {
    // Get all module data so we can find dependents and sort.
    $module_data = system_rebuild_module_data();
    // Create an associative array with weights as values.
    $module_list = array_flip(array_values($module_list));

    while (list($module) = each($module_list)) {
      if (!isset($module_data[$module]) || !$module_data[$module]->status) {
        // This module doesn't exist or is already disabled, skip it.
        unset($module_list[$module]);
        continue;
      }
      $module_list[$module] = $module_data[$module]->sort;

      // Add dependent modules to the list, with a placeholder weight.
      // The new modules will be processed as the while loop continues.
      foreach ($module_data[$module]->required_by as $dependent => $dependent_data) {
        if (!isset($module_list[$dependent]) && !strstr($module_data[$dependent]->filename, '.profile')) {
          $module_list[$dependent] = 0;
        }
      }
    }

    // Sort the module list by pre-calculated weights.
    asort($module_list);
    $module_list = array_keys($module_list);
  }

449
  $invoke_modules = array();
450

451 452
  foreach ($module_list as $module) {
    if (module_exists($module)) {
453 454 455 456 457
      // Check if node_access table needs rebuilding.
      if (!node_access_needs_rebuild() && module_hook($module, 'node_grants')) {
        node_access_needs_rebuild(TRUE);
      }

458 459
      module_load_install($module);
      module_invoke($module, 'disable');
460 461 462 463 464
      db_update('system')
        ->fields(array('status' => 0))
        ->condition('type', 'module')
        ->condition('name', $module)
        ->execute();
465
      $invoke_modules[] = $module;
466
      watchdog('system', '%module module disabled.', array('%module' => $module), WATCHDOG_INFO);
467
    }
Steven Wittens's avatar
Steven Wittens committed
468
  }
469 470

  if (!empty($invoke_modules)) {
471
    // Refresh the module list to exclude the disabled modules.
472
    system_list_reset();
473 474
    module_list(TRUE);
    module_implements('', FALSE, TRUE);
475
    // Invoke hook_modules_disabled before disabling modules,
476 477
    // so we can still call module hooks to get information.
    module_invoke_all('modules_disabled', $invoke_modules);
478 479
    // Update the registry to remove the newly-disabled module.
    registry_update();
480
    _system_update_bootstrap_status();
Steven Wittens's avatar
Steven Wittens committed
481
  }
482

483
  // If there remains no more node_access module, rebuilding will be
484 485 486 487
  // straightforward, we can do it right now.
  if (node_access_needs_rebuild() && count(module_implements('node_grants')) == 0) {
    node_access_rebuild();
  }
Steven Wittens's avatar
Steven Wittens committed
488 489
}

490 491
/**
 * @defgroup hooks Hooks
492 493
 * @{
 * Allow modules to interact with the Drupal core.
494 495
 *
 * Drupal's module system is based on the concept of "hooks". A hook is a PHP
496 497 498
 * function that is named foo_bar(), where "foo" is the name of the module
 * (whose filename is thus foo.module) and "bar" is the name of the hook. Each
 * hook has a defined set of parameters and a specified result type.
499
 *
500 501 502
 * To extend Drupal, a module need simply implement a hook. When Drupal wishes
 * to allow intervention from modules, it determines which modules implement a
 * hook and calls that hook in all enabled modules that implement it.
503 504 505
 *
 * The available hooks to implement are explained here in the Hooks section of
 * the developer documentation. The string "hook" is used as a placeholder for
506 507 508
 * the module name in the hook definitions. For example, if the module file is
 * called example.module, then hook_help() as implemented by that module would
 * be defined as example_help().
509
 *
510 511 512 513
 * The example functions included are not part of the Drupal core, they are
 * just models that you can modify. Only the hooks implemented within modules
 * are executed when running Drupal.
 *
514
 * See also @link themeable the themeable group page. @endlink
515 516 517 518 519 520 521 522 523 524 525 526 527 528
 */

/**
 * Determine whether a module implements a hook.
 *
 * @param $module
 *   The name of the module (without the .module extension).
 * @param $hook
 *   The name of the hook (e.g. "help" or "menu").
 * @return
 *   TRUE if the module is both installed and enabled, and the hook is
 *   implemented in that module.
 */
function module_hook($module, $hook) {
529
  return function_exists($module . '_' . $hook);
530 531
}

532 533 534 535
/**
 * Determine which modules are implementing a hook.
 *
 * @param $hook
536
 *   The name of the hook (e.g. "help" or "menu").
537
 * @param $sort
538 539
 *   By default, modules are ordered by weight and filename, settings this option
 *   to TRUE, module list will be ordered by module name.
540
 * @param $reset
541 542 543
 *   For internal use only: Whether to force the stored list of hook
 *   implementations to be regenerated (such as after enabling a new module,
 *   before processing hook_enable).
544
 *
545 546
 * @return
 *   An array with the names of the modules which are implementing this hook.
547
 *
548
 * @see module_implements_write_cache()
549
 */
550
function module_implements($hook, $sort = FALSE, $reset = FALSE) {
551
  // Use the advanced drupal_static() pattern, since this is called very often.
552 553 554 555 556
  static $drupal_static_fast;
  if (!isset($drupal_static_fast)) {
    $drupal_static_fast['implementations'] = &drupal_static(__FUNCTION__);
  }
  $implementations = &$drupal_static_fast['implementations'];
557

558 559 560 561 562 563 564 565 566 567 568
  // We maintain a persistent cache of hook implementations in addition to the
  // static cache to avoid looping through every module and every hook on each
  // request. Benchmarks show that the benefit of this caching outweighs the
  // additional database hit even when using the default database caching
  // backend and only a small number of modules are enabled. The cost of the
  // cache_get() is more or less constant and reduced further when non-database
  // caching backends are used, so there will be more significant gains when a
  // large number of modules are installed or hooks invoked, since this can
  // quickly lead to module_hook() being called several thousand times
  // per request.
  if ($reset) {
569
    $implementations = array();
570
    cache_set('module_implements', array(), 'cache_bootstrap');
571
    drupal_static_reset('module_hook_info');
572
    drupal_static_reset('drupal_alter');
573
    cache_clear_all('hook_info', 'cache_bootstrap');
574
    return;
575 576
  }

577 578
  // Fetch implementations from cache.
  if (empty($implementations)) {
579
    $implementations = cache_get('module_implements', 'cache_bootstrap');
580 581 582 583 584 585 586 587
    if ($implementations === FALSE) {
      $implementations = array();
    }
    else {
      $implementations = $implementations->data;
    }
  }

588
  if (!isset($implementations[$hook])) {
589
    $hook_info = module_hook_info();
590 591 592
    $implementations[$hook] = array();
    $list = module_list(FALSE, FALSE, $sort);
    foreach ($list as $module) {
593 594
      $include_file = isset($hook_info[$hook]['group']) && module_load_include('inc', $module, $module . '.' . $hook_info[$hook]['group']);
      if (module_hook($module, $hook)) {
595
        $implementations[$hook][$module] = $include_file ? $hook_info[$hook]['group'] : FALSE;
596 597 598 599
        // We added something to the cache, so write it when we are done.
        $implementations['#write_cache'] = TRUE;
      }
    }
600 601 602 603 604
    // Allow modules to change the weight of specific implementations but avoid
    // an infinite loop.
    if ($hook != 'module_implements_alter') {
      drupal_alter('module_implements', $implementations[$hook], $hook);
    }
605 606
  }
  else {
607 608 609 610 611 612
    foreach ($implementations[$hook] as $module => $group) {
      // If this hook implementation is stored in a lazy-loaded file, so include
      // that file first.
      if ($group) {
        module_load_include('inc', $module, "$module.$group");
      }
613 614 615 616 617 618 619 620
      // It is possible that a module removed a hook implementation without the
      // implementations cache being rebuilt yet, so we check module_hook() on
      // each request to avoid undefined function errors.
      if (!module_hook($module, $hook)) {
        // Clear out the stale implementation from the cache and force a cache
        // refresh to forget about no longer existing hook implementations.
        unset($implementations[$hook][$module]);
        $implementations['#write_cache'] = TRUE;
621 622
      }
    }
623
  }
624

625 626 627 628 629 630 631 632 633 634
  return array_keys($implementations[$hook]);
}

/**
 * Retrieve a list of what hooks are explicitly declared.
 */
function module_hook_info() {
  $hook_info = &drupal_static(__FUNCTION__, array());

  if (empty($hook_info)) {
635
    $cache = cache_get('hook_info', 'cache_bootstrap');
636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655
    if ($cache === FALSE) {
      // Rebuild the cache and save it.
      // We can't use module_invoke_all() here or it would cause an infinite
      // loop.
      foreach (module_list() as $module) {
        $function = $module . '_hook_info';
        if (function_exists($function)) {
          $result = $function();
          if (isset($result) && is_array($result)) {
            $hook_info = array_merge_recursive($hook_info, $result);
          }
        }
      }
      // We can't use drupal_alter() for the same reason as above.
      foreach (module_list() as $module) {
        $function = $module . '_hook_info_alter';
        if (function_exists($function)) {
          $function($hook_info);
        }
      }
656
      cache_set('hook_info', $hook_info, 'cache_bootstrap');
657 658 659 660 661 662 663
    }
    else {
      $hook_info = $cache->data;
    }
  }

  return $hook_info;
664 665
}

666 667 668 669 670 671 672
/**
 * Writes the hook implementation cache.
 *
 * @see module_implements()
 */
function module_implements_write_cache() {
  $implementations = &drupal_static('module_implements');
673 674 675 676
  // Check whether we need to write the cache. We do not want to cache hooks
  // which are only invoked on HTTP POST requests since these do not need to be
  // optimized as tightly, and not doing so keeps the cache entry smaller.
  if (isset($implementations['#write_cache']) && ($_SERVER['REQUEST_METHOD'] == 'GET' || $_SERVER['REQUEST_METHOD'] == 'HEAD')) {
677
    unset($implementations['#write_cache']);
678
    cache_set('module_implements', $implementations, 'cache_bootstrap');
679 680 681
  }
}

682 683 684 685 686 687 688 689 690 691 692 693
/**
 * Invoke a hook in a particular module.
 *
 * @param $module
 *   The name of the module (without the .module extension).
 * @param $hook
 *   The name of the hook to invoke.
 * @param ...
 *   Arguments to pass to the hook implementation.
 * @return
 *   The return value of the hook implementation.
 */
694 695
function module_invoke() {
  $args = func_get_args();
696 697 698
  $module = $args[0];
  $hook = $args[1];
  unset($args[0], $args[1]);
699
  if (module_hook($module, $hook)) {
700
    return call_user_func_array($module . '_' . $hook, $args);
701 702 703 704 705 706 707 708 709 710 711 712 713
  }
}
/**
 * Invoke a hook in all enabled modules that implement it.
 *
 * @param $hook
 *   The name of the hook to invoke.
 * @param ...
 *   Arguments to pass to the hook.
 * @return
 *   An array of return values of the hook implementations. If modules return
 *   arrays from their implementations, those are merged into one array.
 */
714 715
function module_invoke_all() {
  $args = func_get_args();
716 717
  $hook = $args[0];
  unset($args[0]);
718
  $return = array();
719
  foreach (module_implements($hook) as $module) {
720
    $function = $module . '_' . $hook;
721
    if (function_exists($function)) {
722 723 724 725
      $result = call_user_func_array($function, $args);
      if (isset($result) && is_array($result)) {
        $return = array_merge_recursive($return, $result);
      }
726
      elseif (isset($result)) {
727 728
        $return[] = $result;
      }
729
    }
730 731 732 733 734 735
  }

  return $return;
}

/**
736
 * @} End of "defgroup hooks".
737 738
 */

739 740 741 742
/**
 * Array of modules required by core.
 */
function drupal_required_modules() {
743 744
  $files = drupal_system_listing('/\.info$/', 'modules', 'name', 0);
  $required = array();
745 746 747 748

  // An install profile is required and one must always be loaded.
  $required[] = drupal_get_profile();

749
  foreach ($files as $name => $file) {
750
    $info = drupal_parse_info_file($file->uri);
751 752 753 754
    if (!empty($info) && !empty($info['required']) && $info['required']) {
      $required[] = $name;
    }
  }
755

756
  return $required;
757
}
758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789

/**
 * Hands off alterable variables to type-specific *_alter implementations.
 *
 * This dispatch function hands off the passed in variables to type-specific
 * hook_TYPE_alter() implementations in modules. It ensures a consistent
 * interface for all altering operations.
 *
 * A maximum of 2 alterable arguments is supported. In case more arguments need
 * to be passed and alterable, modules provide additional variables assigned by
 * reference in the last $context argument:
 * @code
 *   $context = array(
 *     'alterable' => &$alterable,
 *     'unalterable' => $unalterable,
 *     'foo' => 'bar',
 *   );
 *   drupal_alter('mymodule_data', $alterable1, $alterable2, $context);
 * @endcode
 *
 * Note that objects are always passed by reference in PHP5. If it is absolutely
 * required that no implementation alters a passed object in $context, then an
 * object needs to be cloned:
 * @code
 *   $context = array(
 *     'unalterable_object' => clone $object,
 *   );
 *   drupal_alter('mymodule_data', $data, $context);
 * @endcode
 *
 * @param $type
 *   A string describing the data type of the alterable $data. 'form', 'links',
790 791 792 793 794 795
 *   'node_content', and so on are several examples. Alternatively can be an
 *   array, in which case hook_TYPE_alter() is invoked for each value in the
 *   array, ordered first by module, and then for each module, in the order of
 *   values in $type. For example, when Form API is using drupal_alter() to
 *   execute both hook_form_alter() and hook_form_FORM_ID_alter()
 *   implementations, it passes array('form', 'form_' . $form_id) for $type.
796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812
 * @param &$data
 *   The primary data to be altered.
 * @param &$context1
 *   (optional) An additional variable that is passed by reference.
 * @param &$context2
 *   (optional) An additional variable that is passed by reference. If more
 *   context needs to be provided to implementations, then this should be an
 *   keyed array as described above.
 */
function drupal_alter($type, &$data, &$context1 = NULL, &$context2 = NULL) {
  // Use the advanced drupal_static() pattern, since this is called very often.
  static $drupal_static_fast;
  if (!isset($drupal_static_fast)) {
    $drupal_static_fast['functions'] = &drupal_static(__FUNCTION__);
  }
  $functions = &$drupal_static_fast['functions'];

813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831
  // Most of the time, $type is passed as a string, so for performance,
  // normalize it to that. When passed as an array, usually the first item in
  // the array is a generic type, and additional items in the array are more
  // specific variants of it, as in the case of array('form', 'form_FORM_ID').
  if (is_array($type)) {
    $cid = implode(',', $type);
    $extra_types = $type;
    $type = array_shift($extra_types);
    // Allow if statements in this function to use the faster isset() rather
    // than !empty() both when $type is passed as a string, or as an array with
    // one item.
    if (empty($extra_types)) {
      unset($extra_types);
    }
  }
  else {
    $cid = $type;
  }

832 833 834
  // Some alter hooks are invoked many times per page request, so statically
  // cache the list of functions to call, and on subsequent calls, iterate
  // through them quickly.
835 836
  if (!isset($functions[$cid])) {
    $functions[$cid] = array();
837
    $hook = $type . '_alter';
838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875
    $modules = module_implements($hook);
    if (!isset($extra_types)) {
      // For the more common case of a single hook, we do not need to call
      // function_exists(), since module_implements() returns only modules with
      // implementations.
      foreach ($modules as $module) {
        $functions[$cid][] = $module . '_' . $hook;
      }
    }
    else {
      // For multiple hooks, we need $modules to contain every module that
      // implements at least one of them.
      $extra_modules = array();
      foreach ($extra_types as $extra_type) {
        $extra_modules = array_merge($extra_modules, module_implements($extra_type . '_alter'));
      }
      // If any modules implement one of the extra hooks that do not implement
      // the primary hook, we need to add them to the $modules array in their
      // appropriate order.
      if (array_diff($extra_modules, $modules)) {
        // Order the modules by the order returned by module_list().
        $modules = array_intersect(module_list(), array_merge($modules, $extra_modules));
      }
      foreach ($modules as $module) {
        // Since $modules is a merged array, for any given module, we do not
        // know whether it has any particular implementation, so we need a
        // function_exists().
        $function = $module . '_' . $hook;
        if (function_exists($function)) {
          $functions[$cid][] = $function;
        }
        foreach ($extra_types as $extra_type) {
          $function = $module . '_' . $extra_type . '_alter';
          if (function_exists($function)) {
            $functions[$cid][] = $function;
          }
        }
      }
876 877 878 879 880 881 882 883 884 885 886 887 888
    }
    // Allow the theme to alter variables after the theme system has been
    // initialized.
    global $theme, $base_theme_info;
    if (isset($theme)) {
      $theme_keys = array();
      foreach ($base_theme_info as $base) {
        $theme_keys[] = $base->name;
      }
      $theme_keys[] = $theme;
      foreach ($theme_keys as $theme_key) {
        $function = $theme_key . '_' . $hook;
        if (function_exists($function)) {
889 890 891 892 893 894 895 896 897
          $functions[$cid][] = $function;
        }
        if (isset($extra_types)) {
          foreach ($extra_types as $extra_type) {
            $function = $theme_key . '_' . $extra_type . '_alter';
            if (function_exists($function)) {
              $functions[$cid][] = $function;
            }
          }
898 899 900 901
        }
      }
    }
  }
902 903

  foreach ($functions[$cid] as $function) {
904 905 906
    $function($data, $context1, $context2);
  }
}
907