drupal/includes/form.inc

<?php
// $Id: form.inc,v 1.392 2009/11/04 04:56:54 webchick Exp $

/**
 * @defgroup forms Form builder functions
 * @{
 * Functions that build an abstract representation of a HTML form.
 *
 * All modules should declare their form builder functions to be in this
 * group and each builder function should reference its validate and submit
 * functions using \@see. Conversely, validate and submit functions should
 * reference the form builder function using \@see. For examples, of this see
 * system_modules_uninstall() or user_pass(), the latter of which has the
 * following in its doxygen documentation:
 *
 * \@ingroup forms
 * \@see user_pass_validate().
 * \@see user_pass_submit().
 *
 * @} End of "defgroup forms".
 */

/**
 * @defgroup form_api 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 and processing an HTML
 * form for modules automatically. For example:
 *
 * @code
 *   // Display the user registration form.
 *   $output = drupal_get_form('user_register_form');
 * @endcode
 *
 * Forms can also be built and submitted programmatically without any user input
 * using the drupal_form_submit() 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
 * @link http://api.drupal.org/api/file/developer/topics/forms_api_reference.html reference @endlink
 * and the @link http://api.drupal.org/api/file/developer/topics/forms_api.html quickstart guide. @endlink
 */

/**
 * Wrapper for drupal_build_form() for use when $form_state is not needed.
 *
 * @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 $form_id values to the
 *   proper form constructor function. Examples may be found in node_forms(),
 *   search_forms(), and user_forms().
 * @param ...
 *   Any additional arguments are passed on to the functions called by
 *   drupal_get_form(), including the unique form constructor function. For
 *   example, the node_edit form requires that a node object is passed in here
 *   when it is called.
 * @return
 *   The form array.
 *
 * @see drupal_build_form()
 */
function drupal_get_form($form_id) {
  $form_state = array();

  $args = func_get_args();
  // Remove $form_id from the arguments.
  array_shift($args);
  $form_state['build_info']['args'] = $args;

  return drupal_build_form($form_id, $form_state);
}

/**
 * Build and process a form based on a form id.
 *
 * The form may also be retrieved from the cache if the form was built in a
 * previous page-load. The form is then passed on for processing, validation
 * and submission if there is proper input.
 *
 * @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 $form_id values to the
 *   proper form constructor function. Examples may be found in node_forms(),
 *   search_forms(), and user_forms().
 * @param &$form_state
 *   An array which stores information about the form. This is passed as a
 *   reference so that the caller can use it to examine what in the form changed
 *   when the form submission process is complete.
 *   The following parameters may be set in $form_state to affect how the form
 *   is rendered:
 *   - build_info: A keyed array of build information that is necessary to
 *     rebuild the form from cache when the original context may no longer be
 *     available:
 *     - args: An array of arguments to pass to the form builder.
 *     - file: An optional include file that contains the form and is
 *       automatically loaded by form_get_cache(). Defaults to the current menu
 *       router item's 'file' definition, if existent.
 *   - input: An array of input that corresponds to $_POST or $_GET, depending
 *     on the 'method' chosen (see below).
 *   - method: The HTTP form method to use for finding the input for this form.
 *     May be 'post' or 'get'. Defaults to 'post'. Note that 'get' method
 *     forms do not use form ids so are always considered to be submitted, which
 *     can have unexpected effects. The 'get' method should only be used on
 *     forms that do not change data, as that is exclusively the domain of post.
 *   - no_redirect: If set to TRUE the form will NOT perform a drupal_goto(),
 *     even if a redirect is set.
 *   - always_process: If TRUE and the method is GET, a form_id is not
 *     necessary. This should only be used on RESTful GET forms that do NOT
 *     write data, as this could lead to security issues. It is useful so that
 *     searches do not need to have a form_id in their query arguments to
 *     trigger the search.
 *   - must_validate: Ordinarily, a form is only validated once but there are
 *     times when a form is resubmitted internally and should be validated
 *     again. Setting this to TRUE will force that to happen. This is most
 *     likely to occur during AHAH or AJAX operations.
 *   - wrapper_callback: Modules that wish to pre-populate certain forms with
 *     common elements, such as back/next/save buttons in multi-step form
 *     wizards, may define a form builder function name that returns a form
 *     structure, which is passed on to the actual form builder function.
 *     Such implementations may either define the 'wrapper_callback' via
 *     hook_forms() or have to invoke drupal_build_form() (instead of
 *     drupal_get_form()) on their own in a custom menu callback to prepare
 *     $form_state accordingly.
 *   Further $form_state properties controlling the redirection behavior after
 *   form submission may be found in drupal_redirect_form().
 *
 * @return
 *   The rendered form or NULL, depending upon the $form_state flags that were set.
 *
 * @see drupal_redirect_form()
 */
function drupal_build_form($form_id, &$form_state) {
  // Ensure some defaults; if already set they will not be overridden.
  $form_state += form_state_defaults();

  if (!isset($form_state['input'])) {
    $form_state['input'] = $form_state['method'] == 'get' ? $_GET : $_POST;
  }

  $cacheable = FALSE;

  if (isset($_SESSION['batch_form_state'])) {
    // We've been redirected here after a batch processing : the form has
    // already been processed, so we grab the post-process $form_state value
    // and move on to form display. See _batch_finished() function.
    $form_state = $_SESSION['batch_form_state'];
    unset($_SESSION['batch_form_state']);
  }
  else {
    // If the incoming input contains a form_build_id, we'll check the
    // cache for a copy of the form in question. If it's there, we don't
    // have to rebuild the form to proceed. In addition, if there is stored
    // form_state data from a previous step, we'll retrieve it so it can
    // be passed on to the form processing code.
    if (isset($form_state['input']['form_id']) && $form_state['input']['form_id'] == $form_id && !empty($form_state['input']['form_build_id'])) {
      $form = form_get_cache($form_state['input']['form_build_id'], $form_state);
    }

    // If the previous bit of code didn't result in a populated $form
    // object, we're hitting the form for the first time and we need
    // to build it from scratch.
    if (!isset($form)) {
      // Record the filepath of the include file containing the original form,
      // so the form builder callbacks can be loaded when the form is being
      // rebuilt from cache on a different path (such as 'system/ajax').
      // @see form_get_cache()
      // menu_get_item() is not available at installation time.
      if (!isset($form_state['build_info']['file']) && !defined('MAINTENANCE_MODE')) {
        $item = menu_get_item();
        if (!empty($item['file'])) {
          $form_state['build_info']['file'] = $item['file'];
        }
      }

      $form = drupal_retrieve_form($form_id, $form_state);
      $form_build_id = 'form-' . md5(uniqid(mt_rand(), TRUE));
      $form['#build_id'] = $form_build_id;

      // Fix the form method, if it is 'get' in $form_state, but not in $form.
      if ($form_state['method'] == 'get' && !isset($form['#method'])) {
        $form['#method'] = 'get';
      }

      drupal_prepare_form($form_id, $form, $form_state);
      // Store a copy of the unprocessed form for caching and indicate that it
      // is cacheable if #cache will be set.
      $original_form = $form;
      $cacheable = TRUE;
    }

    // Now that we know we have a form, we'll process it (validating,
    // submitting, and handling the results returned by its submission
    // handlers. Submit handlers accumulate data in the form_state by
    // altering the $form_state variable, which is passed into them by
    // reference.
    drupal_process_form($form_id, $form, $form_state);

    if ($cacheable && !empty($form_state['cache']) && empty($form['#no_cache'])) {
      // Caching is done past drupal_process_form so #process callbacks can
      // set #cache.
      form_set_cache($form_build_id, $original_form, $form_state);
    }
  }

  // Most simple, single-step forms will be finished by this point --
  // drupal_process_form() usually redirects to another page (or to
  // a 'fresh' copy of the form) once processing is complete. If one
  // of the form's handlers has set $form_state['redirect'] to FALSE,
  // the form will simply be re-rendered with the values still in its
  // fields.
  //
  // If $form_state['storage'] or $form_state['rebuild'] has been set
  // and the form has been submitted, we know that we're in a complex
  // multi-part process of some sort and the form's workflow is NOT
  // complete. We need to construct a fresh copy of the form, passing
  // in the latest $form_state in addition to any other variables passed
  // into drupal_get_form().
  if ((!empty($form_state['storage']) || $form_state['rebuild']) && $form_state['submitted'] && !form_get_errors()) {
    $form = drupal_rebuild_form($form_id, $form_state);
  }

  // Don't override #theme if someone already set it.
  if (!isset($form['#theme'])) {
    drupal_theme_initialize();
    $registry = theme_get_registry();
    if (isset($registry[$form_id])) {
      $form['#theme'] = $form_id;
    }
  }

  return $form;
}

/**
 * Retrieve default values for the $form_state array.
 */
function form_state_defaults() {
  return array(
    'args' => array(),
    'rebuild' => FALSE,
    'redirect' => NULL,
    'build_info' => array(),
    'storage' => NULL,
    'submitted' => FALSE,
    'programmed' => FALSE,
    'cache'=> FALSE,
    'method' => 'post',
    'groups' => array(),
  );
}

/**
 * Retrieves a form, caches it and processes it with an empty $_POST.
 *
 * This function clears $_POST and passes the empty $_POST to the form_builder.
 * To preserve some parts from $_POST, pass them in $form_state.
 *
 * If your AHAH callback simulates the pressing of a button, then your AHAH
 * callback will need to do the same as what drupal_get_form would do when the
 * button is pressed: get the form from the cache, run drupal_process_form over
 * it and then if it needs rebuild, run drupal_rebuild_form over it. Then send
 * back a part of the returned form.
 * $form_state['clicked_button']['#array_parents'] will help you to find which
 * part.
 *
 * @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 constructor function. Examples
 *   may be found in node_forms(), search_forms(), and user_forms().
 * @param $form_state
 *   A keyed array containing the current state of the form. Most
 *   important is the $form_state['storage'] collection.
 * @param $form_build_id
 *   If the AHAH callback calling this function only alters part of the form,
 *   then pass in the existing form_build_id so we can re-cache with the same
 *   csid.
 * @return
 *   The newly built form.
 */
function drupal_rebuild_form($form_id, &$form_state, $form_build_id = NULL) {
  $form = drupal_retrieve_form($form_id, $form_state);

  if (!isset($form_build_id)) {
    // We need a new build_id for the new version of the form.
    $form_build_id = 'form-' . md5(mt_rand());
  }
  $form['#build_id'] = $form_build_id;
  drupal_prepare_form($form_id, $form, $form_state);

  if (empty($form['#no_cache'])) {
    // We cache the form structure so it can be retrieved later for validation.
    // If $form_state['storage'] is populated, we also cache it so that it can
    // be used to resume complex multi-step processes.
    form_set_cache($form_build_id, $form, $form_state);
  }

  // Clear out all post data, as we don't want the previous step's
  // data to pollute this one and trigger validate/submit handling,
  // then process the form for rendering.
  $form_state['input'] = array();

  // Also clear out all group associations as these might be different
  // when rerendering the form.
  $form_state['groups'] = array();

  // Do not call drupal_process_form(), since it would prevent the rebuilt form
  // to submit.
  $form = form_builder($form_id, $form, $form_state);
  return $form;
}

/**
 * Fetch a form from cache.
 */
function form_get_cache($form_build_id, &$form_state) {
  if ($cached = cache_get('form_' . $form_build_id, 'cache_form')) {
    $form = $cached->data;

    global $user;
    if ((isset($form['#cache_token']) && drupal_valid_token($form['#cache_token'])) || (!isset($form['#cache_token']) && !$user->uid)) {
      if ($cached = cache_get('form_state_' . $form_build_id, 'cache_form')) {
        // Re-populate $form_state for subsequent rebuilds.
        $form_state['build_info'] = $cached->data['build_info'];
        $form_state['storage'] = $cached->data['storage'];

        // If the original form is contained in an include file, load the file.
        // @see drupal_build_form()
        if (!empty($form_state['build_info']['file']) && file_exists($form_state['build_info']['file'])) {
          require_once DRUPAL_ROOT . '/' . $form_state['build_info']['file'];
        }
      }
      return $form;
    }
  }
}

/**
 * Store a form in the cache.
 */
function form_set_cache($form_build_id, $form, $form_state) {
  // 6 hours cache life time for forms should be plenty.
  $expire = 21600;
  global $user;
  if ($user->uid) {
    $form['#cache_token'] = drupal_get_token();
  }
  cache_set('form_' . $form_build_id, $form, 'cache_form', REQUEST_TIME + $expire);
  if (!empty($form_state['build_info']) || !empty($form_state['storage'])) {
    $data = array(
      'build_info' => $form_state['build_info'],
      'storage' => $form_state['storage'],
    );
    cache_set('form_state_' . $form_build_id, $data, 'cache_form', REQUEST_TIME + $expire);
  }
}

/**
 * Retrieves a form using a form_id, populates it with $form_state['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 constructor function. Examples
 *   may be found in node_forms(), search_forms(), and user_forms().
 * @param $form_state
 *   A keyed array containing the current state of the form. Most
 *   important is the $form_state['values'] collection, a tree of data
 *   used to simulate the incoming $_POST information from a user's
 *   form submission.
 * @param ...
 *   Any additional arguments are passed on to the functions called by
 *   drupal_form_submit(), including the unique form constructor function.
 *   For example, the node_edit form requires that a node object be passed
 *   in here when it is called.
 * For example:
 *
 * @code
 * // register a new user
 * $form_state = array();
 * $form_state['values']['name'] = 'robo-user';
 * $form_state['values']['mail'] = 'robouser@example.com';
 * $form_state['values']['pass'] = 'password';
 * $form_state['values']['op'] = t('Create new account');
 * drupal_form_submit('user_register_form', $form_state);
 *
 * // Create a new node
 * $form_state = array();
 * module_load_include('inc', 'node', 'node.pages');
 * $node = array('type' => 'story');
 * $form_state['values']['title'] = 'My node';
 * $form_state['values']['body'] = 'This is the body text!';
 * $form_state['values']['name'] = 'robo-user';
 * $form_state['values']['op'] = t('Save');
 * drupal_form_submit('story_node_form', $form_state, (object)$node);
 * @endcode
 */
function drupal_form_submit($form_id, &$form_state) {
  if (!isset($form_state['build_info']['args'])) {
    $args = func_get_args();
    array_shift($args);
    array_shift($args);
    $form_state['build_info']['args'] = $args;
  }

  $form = drupal_retrieve_form($form_id, $form_state);
  $form_state['input'] = $form_state['values'];
  $form_state['programmed'] = TRUE;
  // Programmed forms are always submitted.
  $form_state['submitted'] = TRUE;
  // Merge in default values.
  $form_state += form_state_defaults();

  drupal_prepare_form($form_id, $form, $form_state);
  drupal_process_form($form_id, $form, $form_state);
}

/**
 * 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 constructor function.
 * @param $form_state
 *   A keyed array containing the current state of the form.
 * @param ...
 *   Any additional arguments needed by the unique form constructor
 *   function. Generally, these are any arguments passed into the
 *   drupal_get_form() or drupal_form_submit() functions after the first
 *   argument. If a module implements hook_forms(), it can examine
 *   these additional arguments and conditionally return different
 *   builder functions as well.
 */
function drupal_retrieve_form($form_id, &$form_state) {
  $forms = &drupal_static(__FUNCTION__);

  // We save two copies of the incoming arguments: one for modules to use
  // when mapping form ids to constructor functions, and another to pass to
  // the constructor function itself.
  $args = $form_state['build_info']['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 constructor function,
    // such as the node editing form, modules can implement hook_forms(). It
    // maps one or more form_ids to the correct constructor 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', $form_id, $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'];
    }
    // In case $form_state['wrapper_callback'] is not defined already, we also
    // allow hook_forms() to define one.
    if (!isset($form_state['wrapper_callback']) && isset($form_definition['wrapper_callback'])) {
      $form_state['wrapper_callback'] = $form_definition['wrapper_callback'];
    }
  }

  $form = array();
  // We need to pass $form_state by reference in order for forms to modify it,
  // since call_user_func_array() requires that referenced variables are passed
  // explicitly.
  $args = array_merge(array($form, &$form_state), $args);

  // When the passed $form_state (not using drupal_get_form()) defines a
  // 'wrapper_callback', then it requests to invoke a separate (wrapping) form
  // builder function to pre-populate the $form array with form elements, which
  // the actual form builder function ($callback) expects. This allows for
  // pre-populating a form with common elements for certain forms, such as
  // back/next/save buttons in multi-step form wizards.
  // @see drupal_build_form()
  if (isset($form_state['wrapper_callback']) && function_exists($form_state['wrapper_callback'])) {
    $form = call_user_func_array($form_state['wrapper_callback'], $args);
    // Put the prepopulated $form into $args.
    $args[0] = $form;
  }

  // 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);
  $form['#form_id'] = $form_id;

  return $form;
}

/**
 * Processes a form submission.
 *
 * 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.
 * @param $form_state
 *   A keyed array containing the current state of the form. This
 *   includes the current persistent storage data for the form, and
 *   any data passed along by earlier steps when displaying a
 *   multi-step form. Additional information, like the sanitized $_POST
 *   data, is also accumulated here.
 */
function drupal_process_form($form_id, &$form, &$form_state) {
  $form_state['values'] = array();

  // With $_GET, these forms are always submitted if requested.
  if ($form_state['method'] == 'get' && !empty($form_state['always_process'])) {
    if (!isset($form_state['input']['form_build_id'])) {
      $form_state['input']['form_build_id'] = $form['#build_id'];
    }
    if (!isset($form_state['input']['form_id'])) {
      $form_state['input']['form_id'] = $form_id;
    }
    if (!isset($form_state['input']['form_token']) && isset($form['#token'])) {
      $form_state['input']['form_token'] = drupal_get_token($form['#token']);
    }
  }

  // Build the form.
  $form = form_builder($form_id, $form, $form_state);

  // Only process the input if we have a correct form submission.
  if ($form_state['process_input']) {
    drupal_validate_form($form_id, $form, $form_state);

    // drupal_html_id() maintains a cache of element IDs it has seen,
    // so it can prevent duplicates. We want to be sure we reset that
    // cache when a form is processed, so scenarios that result in
    // the form being built behind the scenes and again for the
    // browser don't increment all the element IDs needlessly.
    drupal_static_reset('drupal_html_id');

    if ($form_state['submitted'] && !form_get_errors() && !$form_state['rebuild']) {
      // Execute form submit handlers.
      form_execute_handlers('submit', $form, $form_state);

      // We'll clear out the cached copies of the form and its stored data
      // here, as we've finished with them. The in-memory copies are still
      // here, though.
      if (variable_get('cache', CACHE_DISABLED) == CACHE_DISABLED && !empty($form_state['values']['form_build_id'])) {
        cache_clear_all('form_' . $form_state['values']['form_build_id'], 'cache_form');
        cache_clear_all('storage_' . $form_state['values']['form_build_id'], 'cache_form');
      }

      // If batches were set in the submit handlers, we process them now,
      // possibly ending execution. We make sure we do not react to the batch
      // that is already being processed (if a batch operation performs a
      // drupal_form_submit).
      if ($batch =& batch_get() && !isset($batch['current_set'])) {
        // The batch uses its own copies of $form and $form_state for
        // late execution of submit handlers and post-batch redirection.
        $batch['form'] = $form;
        $batch['form_state'] = $form_state;
        $batch['progressive'] = !$form_state['programmed'];
        batch_process();
        // Execution continues only for programmatic forms.
        // For 'regular' forms, we get redirected to the batch processing
        // page. Form redirection will be handled in _batch_finished(),
        // after the batch is processed.
      }

      // Set a flag to indicate the the form has been processed and executed.
      $form_state['executed'] = TRUE;

      // Redirect the form based on values in $form_state.
      drupal_redirect_form($form_state);
    }
  }
}

/**
 * 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.
 * @param $form_state
 *   A keyed array containing the current state of the form. Passed
 *   in here so that hook_form_alter() calls can use it, as well.
 */
function drupal_prepare_form($form_id, &$form, &$form_state) {
  global $user;

  $form['#type'] = 'form';
  $form_state['programmed'] = isset($form_state['programmed']) ? $form_state['programmed'] : FALSE;

  if (isset($form['#build_id'])) {
    $form['form_build_id'] = array(
      '#type' => 'hidden',
      '#value' => $form['#build_id'],
      '#id' => $form['#build_id'],
      '#name' => 'form_build_id',
    );
  }

  // 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 || $form_state['programmed']) {
      unset($form['#token']);
    }
    else {
      $form['form_token'] = array('#type' => 'token', '#default_value' => drupal_get_token($form['#token']));
    }
  }
  elseif (isset($user->uid) && $user->uid && !$form_state['programmed']) {
    $form['#token'] = $form_id;
    $form['form_token'] = array(
      '#id' => drupal_html_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' => $form_id,
      '#id' => drupal_html_id("edit-$form_id"),
    );
  }
  if (!isset($form['#id'])) {
    $form['#id'] = drupal_html_id($form_id);
  }

  $form += element_info('form');
  $form += array('#tree' => FALSE, '#parents' => array());

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

  if (!isset($form['#submit'])) {
    if (function_exists($form_id . '_submit')) {
      // We set submit here so that it can be altered.
      $form['#submit'] = array($form_id . '_submit');
    }
  }

  // Invoke hook_form_FORM_ID_alter() implementations.
  drupal_alter('form_' . $form_id, $form, $form_state);

  // Invoke hook_form_alter() implementations.
  drupal_alter('form', $form, $form_state, $form_id);
}


/**
 * Validates user-submitted form data from the $form_state 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.
 * @param $form_state
 *   A keyed array containing the current state of the form. The current
 *   user-submitted data is stored in $form_state['values'], though
 *   form validation functions are passed an explicit copy of the
 *   values for the sake of simplicity. Validation handlers can also
 *   $form_state to pass information on to submit handlers. For example:
 *     $form_state['data_for_submision'] = $data;
 *   This technique is useful when validation requires file parsing,
 *   web service requests, or other expensive requests that should
 *   not be repeated in the submission step.
 */
function drupal_validate_form($form_id, $form, &$form_state) {
  $validated_forms = &drupal_static(__FUNCTION__, array());

  if (isset($validated_forms[$form_id]) && empty($form_state['must_validate'])) {
    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_state['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_state, $form_id);
  $validated_forms[$form_id] = TRUE;
}

/**
 * Redirects the user to a URL after a form has been processed.
 *
 * After a form was executed, the data in $form_state controls whether the form
 * is redirected. By default, we redirect to a new destination page. The path of
 * the destination page can be set in $form_state['redirect']. If that is not
 * set, the user is redirected to the current page to display a fresh,
 * unpopulated copy of the form.
 *
 * There are several triggers that may prevent a redirection though:
 * - If $form_state['redirect'] is FALSE, a form builder function or form
 *   validation/submit handler does not want a user to be redirected, which
 *   means that drupal_goto() is not invoked. For most forms, the redirection
 *   logic will be the same regardless of whether $form_state['redirect'] is
 *   undefined or FALSE. However, in case it was not defined and the current
 *   request contains a 'destination' query string, drupal_goto() will redirect
 *   to that given destination instead. Only setting $form_state['redirect'] to
 *   FALSE will prevent any redirection.
 * - If $form_state['no_redirect'] is TRUE, then the callback that originally
 *   built the form explicitly disallows any redirection, regardless of the
 *   redirection value in $form_state['redirect']. For example, ajax_get_form()
 *   defines $form_state['no_redirect'] when building a form in an AJAX
 *   callback to prevent any redirection. $form_state['no_redirect'] should NOT
 *   be altered by form builder functions or form validation/submit handlers.
 * - If $form_state['programmed'] is TRUE, the form submission was usually
 *   invoked via drupal_form_submit(), so any redirection would break the script
 *   that invoked drupal_form_submit().
 * - If $form_state['rebuild'] is TRUE or $form_state['storage'] is populated,
 *   the form is most probably a multi-step form and needs to be rebuilt without
 *   redirection.
 *
 * @param $form_state
 *   A keyed array containing the current state of the form.
 *
 * @see drupal_process_form()
 * @see drupal_build_form()
 */
function drupal_redirect_form($form_state) {
  // Skip redirection for form submissions invoked via drupal_form_submit().
  if (!empty($form_state['programmed'])) {
    return;
  }
  // Skip redirection for multi-step forms.
  if (!empty($form_state['rebuild']) || !empty($form_state['storage'])) {
    return;
  }
  // Skip redirection if it was explicitly disallowed.
  if (!empty($form_state['no_redirect'])) {
    return;
  }
  // Only invoke drupal_goto() if redirect value was not set to FALSE.
  if (!isset($form_state['redirect']) || $form_state['redirect'] !== FALSE) {
    if (isset($form_state['redirect'])) {
      if (is_array($form_state['redirect'])) {
        call_user_func_array('drupal_goto', $form_state['redirect']);
      }
      else {
        // This function can be called from the installer, which guarantees
        // that $redirect will always be a string, so catch that case here
        // and use the appropriate redirect function.
        $function = drupal_installation_attempted() ? 'install_goto' : 'drupal_goto';
        $function($form_state['redirect']);
      }
    }
    drupal_goto($_GET['q']);
  }
}

/**
 * Performs validation on form elements. First ensures required fields are
 * completed, #maxlength is not exceeded, and selected options were in the
 * list of options given to the user. Then calls user-defined validators.
 *
 * @param $elements
 *   An associative array containing the structure of the form.
 * @param $form_state
 *   A keyed array containing the current state of the form. The current
 *   user-submitted data is stored in $form_state['values'], though
 *   form validation functions are passed an explicit copy of the
 *   values for the sake of simplicity. Validation handlers can also
 *   $form_state to pass information on to submit handlers. For example:
 *     $form_state['data_for_submision'] = $data;
 *   This technique is useful when validation requires file parsing,
 *   web service requests, or other expensive requests that should
 *   not be repeated in the submission step.
 * @param $form_id
 *   A unique string identifying the form for validation, submission,
 *   theming, and hook_form_alter functions.
 */
function _form_validate($elements, &$form_state, $form_id = NULL) {
  // Also used in the installer, pre-database setup.
  $t = get_t();

  // Recurse through all children.
  foreach (element_children($elements) as $key) {
    if (isset($elements[$key]) && $elements[$key]) {
      _form_validate($elements[$key], $form_state);
    }
  }
  // Validate the current input.
  if (!isset($elements['#validated']) || !$elements['#validated']) {
    if (isset($elements['#needs_validation'])) {
      // Make sure a value is passed when the field is required.
      // A simple call to empty() will not cut it here as some fields, like
      // checkboxes, can return a valid value of '0'. Instead, check the
      // length if it's a string, and the item count if it's an array.
      if ($elements['#required'] && (!count($elements['#value']) || (is_string($elements['#value']) && strlen(trim($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']))));
      }

      if (isset($elements['#options']) && isset($elements['#value'])) {
        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', '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', 'Illegal choice %choice in %name element.', array('%choice' => $elements['#value'], '%name' => empty($elements['#title']) ? $elements['#parents'][0] : $elements['#title']), WATCHDOG_ERROR);
        }
      }
    }

    // Call user-defined form level validators.
    if (isset($form_id)) {
      form_execute_handlers('validate', $elements, $form_state);
    }
    // Call any element-specific validators. These must act on the element
    // #value data.
    elseif (isset($elements['#element_validate'])) {
      foreach ($elements['#element_validate'] as $function) {
        if (function_exists($function))  {
          $function($elements, $form_state, $form_state['complete form']);
        }
      }
    }
    $elements['#validated'] = TRUE;
  }
}

/**
 * A helper function used to execute custom validation and submission
 * handlers for a given form. Button-specific handlers are checked
 * first. If none exist, the function falls back to form-level handlers.
 *
 * @param $type
 *   The type of handler to execute. 'validate' or 'submit' are the
 *   defaults used by Form API.
 * @param $form
 *   An associative array containing the structure of the form.
 * @param $form_state
 *   A keyed array containing the current state of the form. If the user
 *   submitted the form by clicking a button with custom handler functions
 *   defined, those handlers will be stored here.
 */
function form_execute_handlers($type, &$form, &$form_state) {
  $return = FALSE;
  if (isset($form_state[$type . '_handlers'])) {
    $handlers = $form_state[$type . '_handlers'];
  }
  elseif (isset($form['#' . $type])) {
    $handlers = $form['#' . $type];
  }
  else {
    $handlers = array();
  }

  foreach ($handlers as $function) {
    if (function_exists($function))  {
      // Check to see if a previous _submit handler has set a batch, but
      // make sure we do not react to a batch that is already being processed
      // (for instance if a batch operation performs a drupal_form_submit()).
      if ($type == 'submit' && ($batch =& batch_get()) && !isset($batch['current_set'])) {
        // Some previous _submit handler has set a batch. We store the call
        // in a special 'control' batch set, for execution at the correct
        // time during the batch processing workflow.
        $batch['sets'][] = array('form_submit' => $function);
      }
      else {
        $function($form, $form_state);
      }
      $return = TRUE;
    }
  }
  return $return;
}

/**
 * File an error against a form element.
 *
 * @param $name
 *   The name of the form element. If the #parents property of your form
 *   element is array('foo', 'bar', 'baz') then you may set an error on 'foo'
 *   or 'foo][bar][baz'. Setting an error on 'foo' sets an error for every
 *   element where the #parents array starts with 'foo'.
 * @param $message
 *   The error message to present to the user.
 * @param $reset
 *   Reset the form errors static cache.
 * @return
 *   Never use the return value of this function, use form_get_errors and
 *   form_get_error instead.
 */
function form_set_error($name = NULL, $message = '') {
  $form = &drupal_static(__FUNCTION__, array());
  if (isset($name) && !isset($form[$name])) {
    $form[$name] = $message;
    if ($message) {
      drupal_set_message($message, 'error');
    }
  }
  return $form;
}

/**
 * Clear all errors against all form elements made by form_set_error().
 */
function form_clear_error() {
  drupal_static_reset('form_set_error');
}

/**
 * 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 = '') {
  form_set_error(implode('][', $element['#parents']), $message);
}

/**
 * Walk through the structured form array, adding any required
 * properties to each element and mapping the incoming input
 * data to the proper elements. Also, execute any #process handlers
 * attached to a specific element.
 *
 * @param $form_id
 *   A unique string identifying the form for validation, submission,
 *   theming, and hook_form_alter functions.
 * @param $element
 *   An associative array containing the structure of the current element.
 * @param $form_state
 *   A keyed array containing the current state of the form. In this
 *   context, it is used to accumulate information about which button
 *   was clicked when the form was submitted, as well as the sanitized
 *   $_POST data.
 */
function form_builder($form_id, $element, &$form_state) {
  // Initialize as unprocessed.
  $element['#processed'] = FALSE;

  // Use element defaults.
  if ((!empty($element['#type'])) && ($info = element_info($element['#type']))) {
    // Overlay $info onto $element, retaining preexisting keys in $element.
    $element += $info;
    $element['#defaults_loaded'] = TRUE;
  }

  // Special handling if we're on the top level form element.
  if (isset($element['#type']) && $element['#type'] == 'form') {
    if (!empty($element['#https']) && variable_get('https', FALSE) &&
        !url_is_external($element['#action'])) {
      global $base_root;

      // Not an external URL so ensure that it is secure.
      $element['#action'] = str_replace('http://', 'https://', $base_root) . $element['#action'];
    }

    // Store a complete copy of the form in form_state prior to building the form.
    $form_state['complete form'] = $element;
    // Set a flag if we have a correct form submission. This is always TRUE for
    // programmed forms coming from drupal_form_submit(), or if the form_id coming
    // from the POST data is set and matches the current form_id.
    if ($form_state['programmed'] || (!empty($form_state['input']) && (isset($form_state['input']['form_id']) && ($form_state['input']['form_id'] == $form_id)))) {
      $form_state['process_input'] = TRUE;
    }
    else {
      $form_state['process_input'] = FALSE;
    }
  }

  if (!isset($element['#id'])) {
    $element['#id'] = drupal_html_id('edit-' . implode('-', $element['#parents']));
  }
  // Handle input elements.
  if (!empty($element['#input'])) {
    _form_builder_handle_input_element($form_id, $element, $form_state);
  }
  // Allow for elements to expand to multiple elements, e.g., radios,
  // checkboxes and files.
  if (isset($element['#process']) && !$element['#processed']) {
    foreach ($element['#process'] as $process) {
      if (function_exists($process)) {
        $element = $process($element, $form_state, $form_state['complete form']);
      }
    }
    $element['#processed'] = TRUE;
  }

  // We start off assuming all form elements are in the correct order.
  $element['#sorted'] = TRUE;

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

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

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

    // Assign a decimal placeholder weight to preserve original array order.
    if (!isset($element[$key]['#weight'])) {
      $element[$key]['#weight'] = $count/1000;
    }
    else {
      // If one of the child elements has a weight then we will need to sort
      // later.
      unset($element['#sorted']);
    }
    $element[$key] = form_builder($form_id, $element[$key], $form_state);
    $count++;
  }

  // The #after_build flag allows any piece of a form to be altered
  // after normal input parsing has been completed.
  if (isset($element['#after_build']) && !isset($element['#after_build_done'])) {
    foreach ($element['#after_build'] as $function) {
      $element = $function($element, $form_state);
      $element['#after_build_done'] = TRUE;
    }
  }

  // Now that we've processed everything, we can go back to handle the funky
  // Internet Explorer button-click scenario.
  _form_builder_ie_cleanup($element, $form_state);

  // If some callback set #cache, we need to flip a flag so later it
  // can be found.
  if (!empty($element['#cache'])) {
    $form_state['cache'] = $element['#cache'];
  }

  // If there is a file element, we need to flip a flag so later the
  // form encoding can be set.
  if (isset($element['#type']) && $element['#type'] == 'file') {
    $form_state['has_file_element'] = TRUE;
  }

  if (isset($element['#type']) && $element['#type'] == 'form') {
    // We are on the top form.
    // If there is a file element, we set the form encoding.
    if (isset($form_state['has_file_element'])) {
      $element['#attributes']['enctype'] = 'multipart/form-data';
    }
    // Update the copy of the complete form for usage in validation handlers.
    $form_state['complete form'] = $element;
  }
  return $element;
}

/**
 * Populate the #value and #name properties of input elements so they
 * can be processed and rendered.
 */
function _form_builder_handle_input_element($form_id, &$element, &$form_state) {
  if (!isset($element['#name'])) {
    $name = array_shift($element['#parents']);
    $element['#name'] = $name;
    if ($element['#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.
      $element['#name'] = 'files[' . $element['#name'] . ']';
    }
    elseif (count($element['#parents'])) {
      $element['#name'] .= '[' . implode('][', $element['#parents']) . ']';
    }
    array_unshift($element['#parents'], $name);
  }

  if (!empty($element['#disabled'])) {
    $element['#attributes']['disabled'] = 'disabled';
  }

  // Set the element's #value property.
  if (!isset($element['#value']) && !array_key_exists('#value', $element)) {
    $value_callback = !empty($element['#value_callback']) ? $element['#value_callback'] : 'form_type_' . $element['#type'] . '_value';

    if ($form_state['programmed'] || ($form_state['process_input'] && (!isset($element['#access']) || $element['#access']))) {
      $input = $form_state['input'];
      foreach ($element['#parents'] as $parent) {
        $input = isset($input[$parent]) ? $input[$parent] : NULL;
      }
      // If we have input for the current element, assign it to the #value property.
      if (!$form_state['programmed'] || isset($input)) {
        // Call #type_value to set the form value;
        if (function_exists($value_callback)) {
          $element['#value'] = $value_callback($element, $input, $form_state);
        }
        if (!isset($element['#value']) && isset($input)) {
          $element['#value'] = $input;
        }
      }
      // Mark all posted values for validation.
      if (isset($element['#value']) || (!empty($element['#required']))) {
        $element['#needs_validation'] = TRUE;
      }
    }
    // Load defaults.
    if (!isset($element['#value'])) {
      // Call #type_value without a second argument to request default_value handling.
      if (function_exists($value_callback)) {
        $element['#value'] = $value_callback($element, FALSE, $form_state);
      }
      // Final catch. If we haven't set a value yet, use the explicit default value.
      // Avoid image buttons (which come with garbage value), so we only get value
      // for the button actually clicked.
      if (!isset($element['#value']) && empty($element['#has_garbage_value'])) {
        $element['#value'] = isset($element['#default_value']) ? $element['#default_value'] : '';
      }
    }
  }

  // Determine which button (if any) was clicked to submit the form.
  // We compare the incoming values with the buttons defined in the form,
  // and flag the one that matches. We have to do some funky tricks to
  // deal with Internet Explorer's handling of single-button forms, though.
  if (!empty($form_state['input']) && isset($element['#executes_submit_callback'])) {
    // First, accumulate a collection of buttons, divided into two bins:
    // those that execute full submit callbacks and those that only validate.
    $button_type = $element['#executes_submit_callback'] ? 'submit' : 'button';
    $form_state['buttons'][$button_type][] = $element;

    if (_form_button_was_clicked($element, $form_state)) {
      $form_state['submitted'] = $form_state['submitted'] || $element['#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'.
      $form_state['values'][$element['#name']] = $element['#value'];
      $form_state['clicked_button'] = $element;

      if (isset($element['#validate'])) {
        $form_state['validate_handlers'] = $element['#validate'];
      }
      if (isset($element['#submit'])) {
        $form_state['submit_handlers'] = $element['#submit'];
      }
    }
  }
  form_set_value($element, $element['#value'], $form_state);
}

/**
 * Helper function to handle the sometimes-convoluted logic of button
 * click detection.
 *
 * In Internet Explorer, if ONLY one submit button is present, AND the
 * enter key is used to submit the form, no form value is sent for it
 * and we'll never detect a match. That special case is handled by
 * _form_builder_ie_cleanup().
 */
function _form_button_was_clicked($form, &$form_state) {
  // First detect normal 'vanilla' button clicks. Traditionally, all
  // standard buttons on a form share the same name (usually 'op'),
  // and the specific return value is used to determine which was
  // clicked. This ONLY works as long as $form['#name'] puts the
  // value at the top level of the tree of $_POST data.
  if (isset($form_state['input'][$form['#name']]) && $form_state['input'][$form['#name']] == $form['#value']) {
    return TRUE;
  }
  // When image buttons are clicked, browsers do NOT pass the form element
  // value in $_POST. Instead they pass an integer representing the
  // coordinates of the click on the button image. This means that image
  // buttons MUST have unique $form['#name'] values, but the details of
  // their $_POST data should be ignored.
  elseif (!empty($form['#has_garbage_value']) && isset($form['#value']) && $form['#value'] !== '') {
    return TRUE;
  }
  return FALSE;
}

/**
 * In IE, if only one submit button is present, AND the enter key is
 * used to submit the form, no form value is sent for it and our normal
 * button detection code will never detect a match. We call this
 * function after all other button-detection is complete to check
 * for the proper conditions, and treat the single button on the form
 * as 'clicked' if they are met.
 */
function _form_builder_ie_cleanup($form, &$form_state) {
  // Quick check to make sure we're always looking at the full form
  // and not a sub-element.
  if (!empty