form.inc

<?php
// $Id$

/**
 * @defgroup form Form generation
 * @{
 * Functions to enable the processing and display of HTML forms.
 *
 * Drupal uses these functions to achieve consistency in its form processing and
 * presentation, while simplifying code and reducing the amount of HTML that
 * must be explicitly generated by modules.
 *
 * The drupal_get_form() function handles retrieving, processing, and
 * displaying a rendered HTML form for modules automatically. For example:
 *
 * // display the user registration form
 * $output = drupal_get_form('user_register');
 *
 * Forms can also be built and submitted programmatically without any user input
 * using the drupal_execute() function.
 *
 *
 * For information on the format of the structured arrays used to define forms,
 * and more detailed explanations of the Form API workflow, see the reference at
 * http://api.drupal.org/api/HEAD/file/developer/topics/forms_api_reference.html
 * and the quickstart guide at
 * http://api.drupal.org/api/HEAD/file/developer/topics/forms_api.html
 */

/**
 * Retrieves a form from a builder function, passes it on for
 * processing, and renders the form or redirects to its destination
 * as appropriate. In multi-step form scenarios, it handles properly
 * processing the values using the previous step's form definition,
 * then rendering the requested step for display.
 *
 * @param $form_id
 *   The unique string identifying the desired form. If a function
 *   with that name exists, it is called to build the form array.
 *   Modules that need to generate the same form (or very similar forms)
 *   using different $form_ids can implement hook_forms(), which maps
 *   different $form_id values to the proper form building function. Examples
 *   may be found in node_forms(), search_forms(), and user_forms().
 * @param ...
 *   Any additional arguments needed by the form building function.
 * @return
 *   The rendered form.
 */
function drupal_get_form($form_id) {
  // In multi-step form scenarios, the incoming $_POST values are not
  // necessarily intended for the current form. We need to build
  // a copy of the previously built form for validation and processing,
  // then go on to the one that was requested if everything works.

  $form_build_id = md5(mt_rand());
  if (isset($_POST['form_build_id']) && isset($_SESSION['form'][$_POST['form_build_id']]['args']) && $_POST['form_id'] == $form_id) {
    // There's a previously stored multi-step form. We should handle
    // IT first.
    $stored = TRUE;
    $args = $_SESSION['form'][$_POST['form_build_id']]['args'];
    $form = call_user_func_array('drupal_retrieve_form', $args);
  }
  else {
    // We're coming in fresh; build things as they would be. If the
    // form's #multistep flag is set, store the build parameters so
    // the same form can be reconstituted for validation.
    $args = func_get_args();
    $form = call_user_func_array('drupal_retrieve_form', $args);
    if (isset($form['#multistep']) && $form['#multistep']) {
      // Clean up old multistep form session data.
      _drupal_clean_form_sessions();
      $_SESSION['form'][$form_build_id] = array('timestamp' => time(), 'args' => $args);
      $form['#build_id'] = $form_build_id;
    }
    $stored = FALSE;
  }

  // Process the form, submit it, and store any errors if necessary.
  drupal_process_form($args[0], $form);

  if ($stored && !form_get_errors()) {
    // If it's a stored form and there were no errors, we processed the
    // stored form successfully. Now we need to build the form that was
    // actually requested. We always pass in the current $_POST values
    // to the builder function, as values from one stage of a multistep
    // form can determine how subsequent steps are displayed.
    $args = func_get_args();
    $args[] = $_POST;
    $form = call_user_func_array('drupal_retrieve_form', $args);
    unset($_SESSION['form'][$_POST['form_build_id']]);
    if (isset($form['#multistep']) && $form['#multistep']) {
      $_SESSION['form'][$form_build_id] = array('timestamp' => time(), 'args' => $args);
      $form['#build_id'] = $form_build_id;
    }
    drupal_prepare_form($args[0], $form);
  }

  return drupal_render_form($args[0], $form);
}


/**
 * Remove form information that's at least a day old from the
 * $_SESSION['form'] array.
 */
function _drupal_clean_form_sessions() {
  if (isset($_SESSION['form'])) {
    foreach ($_SESSION['form'] as $build_id => $data) {
      if ($data['timestamp'] < (time() - 84600)) {
        unset($_SESSION['form'][$build_id]);
      }
    }
  }
}


/**
 * Retrieves a form using a form_id, populates it with $form_values,
 * processes it, and returns any validation errors encountered. This
 * function is the programmatic counterpart to drupal_get_form().
 *
 * @param $form_id
 *   The unique string identifying the desired form. If a function
 *   with that name exists, it is called to build the form array.
 *   Modules that need to generate the same form (or very similar forms)
 *   using different $form_ids can implement hook_forms(), which maps
 *   different $form_id values to the proper form building function. Examples
 *   may be found in node_forms(), search_forms(), and user_forms().
 * @param $form_values
 *   An array of values mirroring the values returned by a given form
 *   when it is submitted by a user.
 * @param ...
 *   Any additional arguments needed by the form building function.
 * @return
 *   Any form validation errors encountered.
 *
 * For example:
 *
 * // register a new user
 * $values['name'] = 'robo-user';
 * $values['mail'] = 'robouser@example.com';
 * $values['pass'] = 'password';
 * drupal_execute('user_register', $values);
 *
 * // Create a new node
 * $node = array('type' => 'story');
 * $values['title'] = 'My node';
 * $values['body'] = 'This is the body text!';
 * $values['name'] = 'robo-user';
 * drupal_execute('story_node_form', $values, $node);
 */
function drupal_execute($form_id, $form_values) {
  $args = func_get_args();

  $form_id = array_shift($args);
  $form_values = array_shift($args);
  array_unshift($args, $form_id);

  if (isset($form_values)) {
    $form = call_user_func_array('drupal_retrieve_form', $args);
    $form['#post'] = $form_values;
    return drupal_process_form($form_id, $form);
  }
}

/**
 * Retrieves the structured array that defines a given form.
 *
 * @param $form_id
 *   The unique string identifying the desired form. If a function
 *   with that name exists, it is called to build the form array.
 *   Modules that need to generate the same form (or very similar forms)
 *   using different $form_ids can implement hook_forms(), which maps
 *   different $form_id values to the proper form building function.
 * @param ...
 *   Any additional arguments needed by the form building function.
 */
function drupal_retrieve_form($form_id) {
  static $forms;

  // We save two copies of the incoming arguments: one for modules to use
  // when mapping form ids to builder functions, and another to pass to
  // the builder function itself. We shift out the first argument -- the
  // $form_id itself -- from the list to pass into the builder function,
  // since it's already known.
  $args = func_get_args();
  $saved_args = $args;
  array_shift($args);

  // We first check to see if there's a function named after the $form_id.
  // If there is, we simply pass the arguments on to it to get the form.
  if (!function_exists($form_id)) {
    // In cases where many form_ids need to share a central builder function,
    // such as the node editing form, modules can implement hook_forms(). It
    // maps one or more form_ids to the correct builder functions.
    //
    // We cache the results of that hook to save time, but that only works
    // for modules that know all their form_ids in advance. (A module that
    // adds a small 'rate this comment' form to each comment in a list
    // would need a unique form_id for each one, for example.)
    //
    // So, we call the hook if $forms isn't yet populated, OR if it doesn't
    // yet have an entry for the requested form_id.
    if (!isset($forms) || !isset($forms[$form_id])) {
      $forms = module_invoke_all('forms', $saved_args);
    }
    $form_definition = $forms[$form_id];
    if (isset($form_definition['callback arguments'])) {
      $args = array_merge($form_definition['callback arguments'], $args);
    }
    if (isset($form_definition['callback'])) {
      $callback = $form_definition['callback'];
    }
  }
  // If $callback was returned by a hook_forms() implementation, call it.
  // Otherwise, call the function named after the form id.
  $form = call_user_func_array(isset($callback) ? $callback : $form_id, $args);

  // We store the original function arguments, rather than the final $arg
  // value, so that form_alter functions can see what was originally
  // passed to drupal_retrieve_form(). This allows the contents of #parameters
  // to be saved and passed in at a later date to recreate the form.
  $form['#parameters'] = $saved_args;
  return $form;
}

/**
 * This function is the heart of form API. The form gets built, validated and in
 * appropriate cases, submitted.
 *
 * @param $form_id
 *   The unique string identifying the current form.
 * @param $form
 *   An associative array containing the structure of the form.
 * @return
 *   The path to redirect the user to upon completion.
 */
function drupal_process_form($form_id, &$form) {
  global $form_values, $form_submitted, $user, $form_button_counter;
  static $saved_globals = array();
  // In some scenarios, this function can be called recursively. Pushing any pre-existing
  // $form_values and form submission data lets us start fresh without clobbering work done
  // in earlier recursive calls.
  array_push($saved_globals, array($form_values, $form_submitted, $form_button_counter));

  $form_values = array();
  $form_submitted = FALSE;
  $form_button_counter = array(0, 0);

  drupal_prepare_form($form_id, $form);
  if (($form['#programmed']) || (!empty($_POST) && (($_POST['form_id'] == $form_id) || ($_POST['form_id'] == $form['#base'])))) {
    drupal_validate_form($form_id, $form);
    // IE does not send a button value when there is only one submit button (and no non-submit buttons)
    // and you submit by pressing enter.
    // In that case we accept a submission without button values.
    if ((($form['#programmed']) || $form_submitted || (!$form_button_counter[0] && $form_button_counter[1])) && !form_get_errors()) {
      $redirect = drupal_submit_form($form_id, $form);
      if (!$form['#programmed']) {
        drupal_redirect_form($form, $redirect);
      }
    }
  }

  // We've finished calling functions that alter the global values, so we can
  // restore the ones that were there before this function was called.
  list($form_values, $form_submitted, $form_button_counter) = array_pop($saved_globals);
  return $redirect;
}

/**
 * Prepares a structured form array by adding required elements,
 * executing any hook_form_alter functions, and optionally inserting
 * a validation token to prevent tampering.
 *
 * @param $form_id
 *   A unique string identifying the form for validation, submission,
 *   theming, and hook_form_alter functions.
 * @param $form
 *   An associative array containing the structure of the form.
 */
function drupal_prepare_form($form_id, &$form) {
  global $user;

  $form['#type'] = 'form';

  if (!isset($form['#post'])) {
    $form['#post'] = $_POST;
    $form['#programmed'] = FALSE;
  }
  else {
    $form['#programmed'] = TRUE;
  }

  // In multi-step form scenarios, this id is used to identify
  // a unique instance of a particular form for retrieval.
  if (isset($form['#build_id'])) {
    $form['form_build_id'] = array(
      '#type' => 'hidden',
      '#value' => $form['#build_id'],
      '#id' => $form['#build_id'],
      '#name' => 'form_build_id',
    );
  }

  // If $base is set, it is used in place of $form_id when constructing validation,
  // submission, and theming functions. Useful for mapping many similar or duplicate
  // forms with different $form_ids to the same processing functions.
  if (isset($form['#base'])) {
    $base = $form['#base'];
  }

  // Add a token, based on either #token or form_id, to any form displayed to authenticated users.
  // This ensures that any submitted form was actually requested previously by the user and protects against
  // cross site request forgeries.

  if (isset($form['#token'])) {
    if ($form['#token'] === FALSE || $user->uid == 0 || $form['#programmed']) {
      unset($form['#token']);
    }
    else {
      $form['form_token'] = array('#type' => 'token', '#default_value' => drupal_get_token($form['#token']));
    }
  }
  else if ($user->uid && !$form['#programmed']) {
    $form['#token'] = $form_id;
    $form['form_token'] = array(
      '#id' => form_clean_id('edit-'. $form_id .'-form-token'),
      '#type' => 'token',
      '#default_value' => drupal_get_token($form['#token']),
    );
  }


  if (isset($form_id)) {
    $form['form_id'] = array('#type' => 'hidden', '#value' => $form_id, '#id' => form_clean_id("edit-$form_id"));
  }
  if (!isset($form['#id'])) {
    $form['#id'] = form_clean_id($form_id);
  }

  $form += _element_info('form');

  if (!isset($form['#validate'])) {
    if (function_exists($form_id .'_validate')) {
      $form['#validate'] = array($form_id .'_validate' => array());
    }
    elseif (function_exists($base .'_validate')) {
      $form['#validate'] = array($base .'_validate' => array());
    }
  }

  if (!isset($form['#submit'])) {
    if (function_exists($form_id .'_submit')) {
      // we set submit here so that it can be altered but use reference for
      // $form_values because it will change later
      $form['#submit'] = array($form_id .'_submit' => array());
    }
    elseif (function_exists($base .'_submit')) {
      $form['#submit'] = array($base .'_submit' => array());
    }
  }

  foreach (module_implements('form_alter') as $module) {
    $function = $module .'_form_alter';
    $function($form_id, $form);
  }

  $form = form_builder($form_id, $form);
}


/**
 * Validates user-submitted form data from a global variable using
 * the validate functions defined in a structured form array.
 *
 * @param $form_id
 *   A unique string identifying the form for validation, submission,
 *   theming, and hook_form_alter functions.
 * @param $form
 *   An associative array containing the structure of the form.
 *
 */
function drupal_validate_form($form_id, $form) {
  global $form_values;
  static $validated_forms = array();

  if (isset($validated_forms[$form_id])) {
    return;
  }

  // If the session token was set by drupal_prepare_form(), ensure that it
  // matches the current user's session
  if (isset($form['#token'])) {
    if (!drupal_valid_token($form_values['form_token'], $form['#token'])) {
      // setting this error will cause the form to fail validation
      form_set_error('form_token', t('Validation error, please try again. If this error persists, please contact the site administrator.'));
    }
  }

  _form_validate($form, $form_id);
  $validated_forms[$form_id] = TRUE;
}

/**
 * Processes user-submitted form data from a global variable using
 * the submit functions defined in a structured form array.
 *
 * @param $form_id
 *   A unique string identifying the form for validation, submission,
 *   theming, and hook_form_alter functions.
 * @param $form
 *   An associative array containing the structure of the form.
 * @return
 *   A string containing the path of the page to display when processing
 *   is complete.
 *
 */
function drupal_submit_form($form_id, $form) {
  global $form_values;
  $default_args = array($form_id, &$form_values);

  if (isset($form['#submit'])) {
    foreach ($form['#submit'] as $function => $args) {
      if (function_exists($function)) {
        $args = array_merge($default_args, (array) $args);
        // Since we can only redirect to one page, only the last redirect will work
        $redirect = call_user_func_array($function, $args);
        if (isset($redirect)) {
          $goto = $redirect;
        }
      }
    }
  }
  return $goto;
}

/**
 * Renders a structured form array into themed HTML.
 *
 * @param $form_id
 *   A unique string identifying the form for validation, submission,
 *   theming, and hook_form_alter functions.
 * @param $form
 *   An associative array containing the structure of the form.
 * @return
 *   A string containing the path of the page to display when processing
 *   is complete.
 *
 */
function drupal_render_form($form_id, &$form) {
  // Don't override #theme if someone already set it.
  if (isset($form['#base'])) {
    $base = $form['#base'];
  }

  if (!isset($form['#theme'])) {
    if (theme_get_function($form_id)) {
      $form['#theme'] = $form_id;
    }
    elseif (theme_get_function($base)) {
      $form['#theme'] = $base;
    }
  }

  if (isset($form['#pre_render'])) {
    foreach ($form['#pre_render'] as $function) {
      if (function_exists($function)) {
        $function($form_id, $form);
      }
    }
  }

  $output = drupal_render($form);
  return $output;
}

/**
 * Redirect the user to a URL after a form has been processed.
 *
 * @param $form
 *   An associative array containing the structure of the form.
 * @param $redirect
 *   An optional string containing the destination path to redirect
 *   to if none is specified by the form.
 *
 */
function drupal_redirect_form($form, $redirect = NULL) {
  if (isset($redirect)) {
    $goto = $redirect;
  }
  if (isset($form['#redirect'])) {
    $goto = $form['#redirect'];
  }
  if ($goto !== FALSE) {
    if (is_array($goto)) {
      call_user_func_array('drupal_goto', $goto);
    }
    elseif (!isset($goto)) {
      drupal_goto($_GET['q']);
    }
    else {
      drupal_goto($goto);
    }
  }
}

function _form_validate($elements, $form_id = NULL) {
  // Recurse through all children.
  foreach (element_children($elements) as $key) {
    if (isset($elements[$key]) && $elements[$key]) {
      _form_validate($elements[$key]);
    }
  }
  /* Validate the current input */
  if (!isset($elements['#validated']) || !$elements['#validated']) {
    if (isset($elements['#needs_validation'])) {
      // An empty textfield returns '' so we use empty(). An empty checkbox
      // and a textfield could return '0' and empty('0') returns TRUE so we
      // need a special check for the '0' string.
      if ($elements['#required'] && empty($elements['#value']) && $elements['#value'] !== '0') {
        form_error($elements, t('!name field is required.', array('!name' => $elements['#title'])));
      }

      // Verify that the value is not longer than #maxlength.
      if (isset($elements['#maxlength']) && drupal_strlen($elements['#value']) > $elements['#maxlength']) {
        form_error($elements, t('!name cannot be longer than %max characters but is currently %length characters long.', array('!name' => empty($elements['#title']) ? $elements['#parents'][0] : $elements['#title'], '%max' => $elements['#maxlength'], '%length' => drupal_strlen($elements['#value']))));
      }

      // Add legal choice check if element has #options. Can be skipped, but then you must validate your own element.
      if (isset($elements['#options']) && isset($elements['#value']) && !isset($elements['#DANGEROUS_SKIP_CHECK'])) {
        if ($elements['#type'] == 'select') {
          $options = form_options_flatten($elements['#options']);
        }
        else {
          $options = $elements['#options'];
        }
        if (is_array($elements['#value'])) {
          $value = $elements['#type'] == 'checkboxes' ? array_keys(array_filter($elements['#value'])) : $elements['#value'];
          foreach ($value as $v) {
            if (!isset($options[$v])) {
              form_error($elements, t('An illegal choice has been detected. Please contact the site administrator.'));
              watchdog('form', t('Illegal choice %choice in !name element.', array('%choice' => $v, '!name' => empty($elements['#title']) ? $elements['#parents'][0] : $elements['#title'])), WATCHDOG_ERROR);
            }
          }
        }
        elseif (!isset($options[$elements['#value']])) {
          form_error($elements, t('An illegal choice has been detected. Please contact the site administrator.'));
          watchdog('form', t('Illegal choice %choice in %name element.', array('%choice' => $elements['#value'], '%name' => empty($elements['#title']) ? $elements['#parents'][0] : $elements['#title'])), WATCHDOG_ERROR);
        }
      }
    }

    // User-applied checks.
    if (isset($elements['#validate'])) {
      foreach ($elements['#validate'] as $function => $args) {
        $args = array_merge(array($elements), $args);
        // for the full form we hand over a copy of $form_values
        if (isset($form_id)) {
          $args = array_merge(array($form_id, $GLOBALS['form_values']), $args);
        }
        if (function_exists($function))  {
          call_user_func_array($function, $args);
        }
      }
    }
    $elements['#validated'] = TRUE;
  }
}

/**
 * File an error against a form element. If the name of the element is
 * edit[foo][bar] then you may pass either foo or foo][bar as $name
 * foo will set an error for all its children.
 */
function form_set_error($name = NULL, $message = '') {
  static $form = array();
  if (isset($name) && !isset($form[$name])) {
    $form[$name] = $message;
    if ($message) {
      drupal_set_message($message, 'error');
    }
  }
  return $form;
}

/**
 * Return an associative array of all errors.
 */
function form_get_errors() {
  $form = form_set_error();
  if (!empty($form)) {
    return $form;
  }
}

/**
 * Return the error message filed against the form with the specified name.
 */
function form_get_error($element) {
  $form = form_set_error();
  $key = $element['#parents'][0];
  if (isset($form[$key])) {
    return $form[$key];
  }
  $key = implode('][', $element['#parents']);
  if (isset($form[$key])) {
    return $form[$key];
  }
}

/**
 * Flag an element as having an error.
 */
function form_error(&$element, $message = '') {
  $element['#error'] = TRUE;
  form_set_error(implode('][', $element['#parents']), $message);
}

/**
 * Adds some required properties to each form element, which are used
 * internally in the form api. This function also automatically assigns
 * the value property from the $edit array, provided the element doesn't
 * already have an assigned value.
 *
 * @param $form_id
 *   A unique string identifying the form for validation, submission,
 *   theming, and hook_form_alter functions.
 * @param $form
 *   An associative array containing the structure of the form.
 */
function form_builder($form_id, $form) {
  global $form_values, $form_submitted, $form_button_counter;

  // Initialize as unprocessed.
  $form['#processed'] = FALSE;

  /* Use element defaults */
  if ((!empty($form['#type'])) && ($info = _element_info($form['#type']))) {
    // overlay $info onto $form, retaining preexisting keys in $form
    $form += $info;
  }

  if (isset($form['#input']) && $form['#input']) {
    if (!isset($form['#name'])) {
      $name = array_shift($form['#parents']);
      $form['#name'] = $name;
      if ($form['#type'] == 'file') {
        // to make it easier to handle $_FILES in file.inc, we place all
        // file fields in the 'files' array. Also, we do not support
        // nested file names
        $form['#name'] = 'files['. $form['#name'] .']';
      }
      elseif (count($form['#parents'])) {
        $form['#name'] .= '['. implode('][', $form['#parents']) .']';
      }
      array_unshift($form['#parents'], $name);
    }
    if (!isset($form['#id'])) {
      $form['#id'] = form_clean_id('edit-'. implode('-', $form['#parents']));
    }

    if (isset($form['#disabled']) && $form['#disabled']) {
      $form['#attributes']['disabled'] = 'disabled';
    }

    if (!isset($form['#value']) && !array_key_exists('#value', $form)) {
      if (($form['#programmed']) || ((!isset($form['#access']) || $form['#access']) && isset($form['#post']) && (isset($form['#post']['form_id']) && $form['#post']['form_id'] == $form_id))) {
        $edit = $form['#post'];
        foreach ($form['#parents'] as $parent) {
          $edit = isset($edit[$parent]) ? $edit[$parent] : NULL;
        }
        if (!$form['#programmed'] || isset($edit)) {
          switch ($form['#type']) {
            case 'checkbox':
              $form['#value'] = !empty($edit) ? $form['#return_value'] : 0;
              break;

            case 'select':
              if (isset($form['#multiple']) && $form['#multiple']) {
                if (isset($edit) && is_array($edit)) {
                  $form['#value'] = drupal_map_assoc($edit);
                }
                else {
                  $form['#value'] = array();
                }
              }
              elseif (isset($edit)) {
                $form['#value'] = $edit;
              }
              break;

            case 'textfield':
              if (isset($edit)) {
                // Equate $edit to the form value to ensure it's marked for validation
                $edit = str_replace(array("\r", "\n"), '', $edit);
                $form['#value'] = $edit;
              }
              break;

            case 'token':
              $form['#value'] = (string)$edit;
              break;

            default:
              if (isset($edit)) {
                $form['#value'] = $edit;
              }
          }
          // Mark all posted values for validation
          if ((isset($form['#value']) && $form['#value'] === $edit) || (isset($form['#required']) && $form['#required'])) {
            $form['#needs_validation'] = TRUE;
          }
        }
      }
      if (!isset($form['#value'])) {
        $function = $form['#type'] . '_value';
        if (function_exists($function)) {
          $function($form);
        }
        else {
          $form['#value'] = isset($form['#default_value']) ? $form['#default_value'] : '';
        }
      }
    }
    if (isset($form['#executes_submit_callback'])) {
      // Count submit and non-submit buttons
      $form_button_counter[$form['#executes_submit_callback']]++;
      // See if a submit button was pressed
      if (isset($form['#post'][$form['#name']]) && $form['#post'][$form['#name']] == $form['#value']) {
        $form_submitted = $form_submitted || $form['#executes_submit_callback'];

        // In most cases, we want to use form_set_value() to manipulate the global variables.
        // In this special case, we want to make sure that the value of this element is listed
        // in $form_variables under 'op'.
        $form_values[$form['#name']] = $form['#value'];
      }
    }
  }

  // Allow for elements to expand to multiple elements, e.g. radios, checkboxes and files.
  if (isset($form['#process']) && !$form['#processed']) {
    foreach ($form['#process'] as $process => $args) {
      if (function_exists($process)) {
        $args = array_merge(array($form), array($edit), $args);
        $form = call_user_func_array($process, $args);
      }
    }
    $form['#processed'] = TRUE;
  }

  // Set the $form_values key that gets passed to validate and submit.
  // We call this after #process gets called so that #process has a
  // chance to update #value if desired.
  if (isset($form['#input']) && $form['#input']) {
    form_set_value($form, $form['#value']);
  }

  // Recurse through all child elements.
  $count  = 0;
  foreach (element_children($form) as $key) {
    $form[$key]['#post'] = $form['#post'];
    $form[$key]['#programmed'] = $form['#programmed'];
    // don't squash an existing tree value
    if (!isset($form[$key]['#tree'])) {
      $form[$key]['#tree'] = $form['#tree'];
    }

    // deny access to child elements if parent is denied
    if (isset($form['#access']) && !$form['#access']) {
      $form[$key]['#access'] = FALSE;
    }

    // don't squash existing parents value
    if (!isset($form[$key]['#parents'])) {
      // Check to see if a tree of child elements is present. If so, continue down the tree if required.
      $form[$key]['#parents'] = $form[$key]['#tree'] && $form['#tree'] ? array_merge($form['#parents'], array($key)) : array($key);
    }

    // Assign a decimal placeholder weight to preserve original array order
    if (!isset($form[$key]['#weight'])) {
      $form[$key]['#weight'] = $count/1000;
    }
    $form[$key] = form_builder($form_id, $form[$key]);
    $count++;
  }

  if (isset($form['#after_build']) && !isset($form['#after_build_done'])) {
    foreach ($form['#after_build'] as $function) {
      if (function_exists($function)) {
        $form = $function($form, $form_values);
      }
    }
    $form['#after_build_done'] = TRUE;
  }

  return $form;
}

/**
 * Use this function to make changes to form values in the form validate
 * phase, so they will be available in the submit phase in $form_values.
 *
 * Specifically, if $form['#parents'] is array('foo', 'bar')
 * and $value is 'baz' then this function will make
 * $form_values['foo']['bar'] to be 'baz'.
 *
 * @param $form
 *   The form item. Keys used: #parents, #value
 * @param $value
 *   The value for the form item.
 */
function form_set_value($form, $value) {
  global $form_values;
  _form_set_value($form_values, $form, $form['#parents'], $value);
}

/**
 * Helper function for form_set_value().
 *
 * We iterate of $parents and create nested arrays for them
 * in $form_values if needed. Then we insert the value in
 * the right array.
 */
function _form_set_value(&$form_values, $form, $parents, $value) {
  $parent = array_shift($parents);
  if (empty($parents)) {
    $form_values[$parent] = $value;
  }
  else {
    if (!isset($form_values[$parent])) {
      $form_values[$parent] = array();
    }
    _form_set_value($form_values[$parent], $form, $parents, $value);
  }
  return $form;
}

/**
 * Retrieve the default properties for the defined element type.
 */
function _element_info($type, $refresh = NULL) {
  static $cache;

  $basic_defaults = array(
    '#description' => NULL,
    '#attributes' => array(),
    '#required' => FALSE,
    '#tree' => FALSE,
    '#parents' => array()
  );
  if (!isset($cache) || $refresh) {
    $cache = array();
    foreach (module_implements('elements') as $module) {
      $elements = module_invoke($module, 'elements');
      if (isset($elements) && is_array($elements)) {
        $cache = array_merge_recursive($cache, $elements);
      }
    }
    if (sizeof($cache)) {
      foreach ($cache as $element_type => $info) {
        $cache[$element_type] = array_merge_recursive($basic_defaults, $info);
      }
    }
  }

  return $cache[$type];
}

function form_options_flatten($array, $reset = TRUE) {
  static $return;

  if ($reset) {
    $return = array();
  }

  foreach ($array as $key => $value) {
    if (is_object($value)) {
      form_options_flatten($value->option, FALSE);
    }
    else if (is_array($value)) {
      form_options_flatten($value, FALSE);
    }
    else {
      $return[$key] = 1;
    }
  }

  return $return;
}

/**
 * Format a dropdown menu or scrolling selection box.
 *
 * @param $element
 *   An associative array containing the properties of the element.
 *   Properties used: title, value, options, description, extra, multiple, required
 * @return
 *   A themed HTML string representing the form element.
 *
 * It is possible to group options together; to do this, change the format of
 * $options to an associative array in which the keys are group labels, and the
 * values are associative arrays in the normal $options format.
 */
function theme_select($element) {
  $select = '';
  $size = $element['#size'] ? ' size="' . $element['#size'] . '"' : '';
  _form_set_class($element, array('form-select'));
  $multiple = isset($element['#multiple']) && $element['#multiple'];
  return theme('form_element', $element, '<select name="'. $element['#name'] .''. ($multiple ? '[]' : '') .'"'. ($multiple ? ' multiple="multiple" ' : '') . drupal_attributes($element['#attributes']) .' id="'. $element['#id'] .'" '. $size .'>'. form_select_options($element) .'</select>');
}

function form_select_options($element, $choices = NULL) {
  if (!isset($choices)) {
    $choices = $element['#options'];
  }
  // array_key_exists() accommodates the rare event where $element['#value'] is NULL.
  // isset() fails in this situation.
  $value_valid = isset($element['#value']) || array_key_exists('#value', $element);
  $value_is_array = is_array($element['#value']);
  $options = '';
  foreach ($choices as $key => $choice) {
    if (is_array($choice)) {
      $options .= '<optgroup label="'. $key .'">';
      $options .= form_select_options($element, $choice);
      $options .= '</optgroup>';
    }
    elseif (is_object($choice)) {
      $options .= form_select_options($element, $choice->option);
    }
    else {
      $key = (string)$key;
      if ($value_valid && ($element['#value'] == $key || ($value_is_array && in_array($key, $element['#value'])))) {
        $selected = ' selected="selected"';
      }
      else {
        $selected = '';
      }
      $options .= '<option value="'. $key .'"'. $selected .'>'. check_plain($choice) .'</option>';
    }
  }
  return $options;
}

/**
 * Format a group of form items.
 *
 * @param $element
 *   An associative array containing the properties of the element.
 *   Properties used: attributes, title, value, description, children, collapsible, collapsed
 * @return
 *   A themed HTML string representing the form item group.
 */
function theme_fieldset($element) {
  if ($element['#collapsible']) {
    drupal_add_js('misc/collapse.js');

    if (!isset($element['#attributes']['class'])) {
      $element['#attributes']['class'] = '';
    }

    $element['#attributes']['class'] .= ' collapsible';
    if ($element['#collapsed']) {
     $element['#attributes']['class'] .= ' collapsed';
    }
  }

  return '<fieldset' . drupal_attributes($element['#attributes']) .'>' . ($element['#title'] ? '<legend>'. $element['#title'] .'</legend>' : '') . ($element['#description'] ? '<div class="description">'. $element['#description'] .'</div>' : '') . $element['#children'] . $element['#value'] . "</fieldset>\n";
}

/**
 * Format a radio button.
 *
 * @param $element
 *   An associative array containing the properties of the element.
 *   Properties used: required, return_value, value, attributes, title, description
 * @return
 *   A themed HTML string representing the form item group.
 */
function theme_radio($element) {
  _form_set_class($element, array('form-radio'));
  $output = '<input type="radio" ';
  $output .= 'name="' . $element['#name'] .'" ';
  $output .= 'value="'. $element['#return_value'] .'" ';
  $output .= ($element['#value'] == $element['#return_value']) ? ' checked="checked" ' : ' ';
  $output .= drupal_attributes($element['#attributes']) .' />';
  if (!is_null($element['#title'])) {
    $output = '<label class="option">'. $output .' '. $element['#title'] .'</label>';
  }

  unset($element['#title']);
  return theme('form_element', $element, $output);
}

/**
 * Format a set of radio buttons.
 *
 * @param $element
 *   An associative array containing the properties of the element.
 *   Properties used: title, value, options, description, required and attributes.
 * @return