Club Drupal

<?php

/**

 * @file

 * Functions for use with Drupal's Ajax framework.

 */

/**

 * @defgroup ajax Ajax framework

 * @{

 * Functions for Drupal's Ajax framework.

 *

 * Drupal's Ajax framework is used to dynamically update parts of a page's HTML

 * based on data from the server. Upon a specified event, such as a button

 * click, a callback function is triggered which performs server-side logic and

 * may return updated markup, which is then replaced on-the-fly with no page

 * refresh necessary.

 *

 * This framework creates a PHP macro language that allows the server to

 * instruct JavaScript to perform actions on the client browser. When using

 * forms, it can be used with the #ajax property.

 * The #ajax property can be used to bind events to the Ajax framework. By

 * default, #ajax uses 'system/ajax' as its path for submission and thus calls

 * ajax_form_callback() and a defined #ajax['callback'] function.

 * However, you may optionally specify a different path to request or a

 * different callback function to invoke, which can return updated HTML or can

 * also return a richer set of

 * @link ajax_commands Ajax framework commands @endlink.

 *

 * Standard form handling is as follows:

 *   - A form element has a #ajax property that includes #ajax['callback'] and

 *     omits #ajax['path']. See below about using #ajax['path'] to implement

 *     advanced use-cases that require something other than standard form

 *     handling.

 *   - On the specified element, Ajax processing is triggered by a change to

 *     that element.

 *   - The browser submits an HTTP POST request to the 'system/ajax' Drupal

 *     path.

 *   - The menu page callback for 'system/ajax', ajax_form_callback(), calls

 *     drupal_process_form() to process the form submission and rebuild the

 *     form if necessary. The form is processed in much the same way as if it

 *     were submitted without Ajax, with the same #process functions and

 *     validation and submission handlers called in either case, making it easy

 *     to create Ajax-enabled forms that degrade gracefully when JavaScript is

 *     disabled.

 *   - After form processing is complete, ajax_form_callback() calls the

 *     function named by #ajax['callback'], which returns the form element that

 *     has been updated and needs to be returned to the browser, or

 *     alternatively, an array of custom Ajax commands.

 *   - The page delivery callback for 'system/ajax', ajax_deliver(), renders the

 *     element returned by #ajax['callback'], and returns the JSON string

 *     created by ajax_render() to the browser.

 *   - The browser unserializes the returned JSON string into an array of

 *     command objects and executes each command, resulting in the old page

 *     content within and including the HTML element specified by

 *     #ajax['wrapper'] being replaced by the new content returned by

 *     #ajax['callback'], using a JavaScript animation effect specified by

 *     #ajax['effect'].

 *

 * A simple example of basic Ajax use from the

 * @link http://drupal.org/project/examples Examples module @endlink follows:

 * @code

 * function main_page() {

 *   return drupal_get_form('ajax_example_simplest');

 * }

 *

 * function ajax_example_simplest($form, &$form_state) {

 *   $form = array();

 *   $form['changethis'] = array(

 *     '#type' => 'select',

 *     '#options' => array(

 *       'one' => 'one',

 *       'two' => 'two',

 *       'three' => 'three',

 *     ),

 *     '#ajax' => array(

 *       'callback' => 'ajax_example_simplest_callback',

 *       'wrapper' => 'replace_textfield_div',

 *      ),

 *   );

 *   // This entire form element will be replaced with an updated value.

 *   $form['replace_textfield'] = array(

 *     '#type' => 'textfield',

 *     '#title' => t("The default value will be changed"),

 *     '#description' => t("Say something about why you chose") . "'" .

 *       (!empty($form_state['values']['changethis'])

 *       ? $form_state['values']['changethis'] : t("Not changed yet")) . "'",

 *     '#prefix' => '<div id="replace_textfield_div">',

 *     '#suffix' => '</div>',

 *   );

 *   return $form;

 * }

 *

 * function ajax_example_simplest_callback($form, $form_state) {

 *   // The form has already been submitted and updated. We can return the replaced

 *   // item as it is.

 *   return $form['replace_textfield'];

 * }

 * @endcode

 *

 * In the above example, the 'changethis' element is Ajax-enabled. The default

 * #ajax['event'] is 'change', so when the 'changethis' element changes,

 * an Ajax call is made. The form is submitted and reprocessed, and then the

 * callback is called. In this case, the form has been automatically

 * built changing $form['replace_textfield']['#description'], so the callback

 * just returns that part of the form.

 *

 * To implement Ajax handling in a form, add '#ajax' to the form

 * definition of a field. That field will trigger an Ajax event when it is

 * clicked (or changed, depending on the kind of field). #ajax supports

 * the following parameters (either 'path' or 'callback' is required at least):

 * - #ajax['callback']: The callback to invoke to handle the server side of the

 *   Ajax event, which will receive a $form and $form_state as arguments, and

 *   returns a renderable array (most often a form or form fragment), an HTML

 *   string, or an array of Ajax commands. If returning a renderable array or

 *   a string, the value will replace the original element named in

 *   #ajax['wrapper'], and

 *   theme_status_messages()

 *   will be prepended to that

 *   element. (If the status messages are not wanted, return an array

 *   of Ajax commands instead.)

 *   #ajax['wrapper']. If an array of Ajax commands is returned, it will be

 *   executed by the calling code.

 * - #ajax['path']: The menu path to use for the request. This is often omitted

 *   and the default is used. This path should map

 *   to a menu page callback that returns data using ajax_render(). Defaults to

 *   'system/ajax', which invokes ajax_form_callback(), eventually calling

 *   the function named in #ajax['callback']. If you use a custom

 *   path, you must set up the menu entry and handle the entire callback in your

 *   own code.

 * - #ajax['wrapper']: The CSS ID of the area to be replaced by the content

 *   returned by the #ajax['callback'] function. The content returned from

 *   the callback will replace the entire element named by #ajax['wrapper'].

 *   The wrapper is usually created using #prefix and #suffix properties in the

 *   form. Note that this is the wrapper ID, not a CSS selector. So to replace

 *   the element referred to by the CSS selector #some-selector on the page,

 *   use #ajax['wrapper'] = 'some-selector', not '#some-selector'.

 * - #ajax['effect']: The jQuery effect to use when placing the new HTML.

 *   Defaults to no effect. Valid options are 'none', 'slide', or 'fade'.

 * - #ajax['speed']: The effect speed to use. Defaults to 'slow'. May be

 *   'slow', 'fast' or a number in milliseconds which represents the length

 *   of time the effect should run.

 * - #ajax['event']: The JavaScript event to respond to. This is normally

 *   selected automatically for the type of form widget being used, and

 *   is only needed if you need to override the default behavior.

 * - #ajax['prevent']: A JavaScript event to prevent when 'event' is triggered.

 *   Defaults to 'click' for #ajax on #type 'submit', 'button', and

 *   'image_button'. Multiple events may be specified separated by spaces.

 *   For example, when binding #ajax behaviors to form buttons, pressing the

 *   ENTER key within a textfield triggers the 'click' event of the form's first

 *   submit button. Triggering Ajax in this situation leads to problems, like

 *   breaking autocomplete textfields. Because of that, Ajax behaviors are bound

 *   to the 'mousedown' event on form buttons by default. However, binding to

 *   'mousedown' rather than 'click' means that it is possible to trigger a

 *   click by pressing the mouse, holding the mouse button down until the Ajax

 *   request is complete and the button is re-enabled, and then releasing the

 *   mouse button. For this case, 'prevent' can be set to 'click', so an

 *   additional event handler is bound to prevent such a click from triggering a

 *   non-Ajax form submission. This also prevents a textfield's ENTER press

 *   triggering a button's non-Ajax form submission behavior.

 * - #ajax['method']: The jQuery method to use to place the new HTML.

 *   Defaults to 'replaceWith'. May be: 'replaceWith', 'append', 'prepend',

 *   'before', 'after', or 'html'. See the

 *   @link http://api.jquery.com/category/manipulation/ jQuery manipulators documentation @endlink

 *   for more information on these methods.

 * - #ajax['progress']: Choose either a throbber or progress bar that is

 *   displayed while awaiting a response from the callback, and add an optional

 *   message. Possible keys: 'type', 'message', 'url', 'interval'.

 *   More information is available in the

 *   @link forms_api_reference.html Form API Reference @endlink

 *

 * In addition to using Form API for doing in-form modification, Ajax may be

 * enabled by adding classes to buttons and links. By adding the 'use-ajax'

 * class to a link, the link will be loaded via an Ajax call. When using this

 * method, the href of the link can contain '/nojs/' as part of the path. When

 * the Ajax framework makes the request, it will convert this to '/ajax/'.

 * The server is then able to easily tell if this request was made through an

 * actual Ajax request or in a degraded state, and respond appropriately.

 *

 * Similarly, submit buttons can be given the class 'use-ajax-submit'. The

 * form will then be submitted via Ajax to the path specified in the #action.

 * Like the ajax-submit class above, this path will have '/nojs/' replaced with

 * '/ajax/' so that the submit handler can tell if the form was submitted

 * in a degraded state or not.

 *

 * When responding to Ajax requests, the server should do what it needs to do

 * for that request, then create a commands array. This commands array will

 * be converted to a JSON object and returned to the client, which will then

 * iterate over the array and process it like a macro language.

 *

 * Each command item is an associative array which will be converted to a

 * command object on the JavaScript side. $command_item['command'] is the type

 * of command, e.g. 'alert' or 'replace', and will correspond to a method in the

 * Drupal.ajax[command] space. The command array may contain any other data that

 * the command needs to process, e.g. 'method', 'selector', 'settings', etc.

 *

 * Commands are usually created with a couple of helper functions, so they

 * look like this:

 * @code

 *   $commands = array();

 *   // Replace the content of '#object-1' on the page with 'some html here'.

 *   $commands[] = ajax_command_replace('#object-1', 'some html here');

 *   // Add a visual "changed" marker to the '#object-1' element.

 *   $commands[] = ajax_command_changed('#object-1');

 *   // Menu 'page callback' and #ajax['callback'] functions are supposed to

 *   // return render arrays. If returning an Ajax commands array, it must be

 *   // encapsulated in a render array structure.

 *   return array('#type' => 'ajax', '#commands' => $commands);

 * @endcode

 *

 * When returning an Ajax command array, it is often useful to have

 * status messages rendered along with other tasks in the command array.

 * In that case the Ajax commands array may be constructed like this:

 * @code

 *   $commands = array();

 *   $commands[] = ajax_command_replace(NULL, $output);

 *   $commands[] = ajax_command_prepend(NULL, theme('status_messages'));

 *   return array('#type' => 'ajax', '#commands' => $commands);

 * @endcode

 *

 * See @link ajax_commands Ajax framework commands @endlink

 */

/**

 * Renders a commands array into JSON.

 *

 * @param $commands

 *   A list of macro commands generated by the use of ajax_command_*()

 *   functions.

 */

function ajax_render($commands = array()) {

  // Although ajax_deliver() does this, some contributed and custom modules

  // render Ajax responses without using that delivery callback.

  ajax_set_verification_header();

  // Ajax responses aren't rendered with html.tpl.php, so we have to call

  // drupal_get_css() and drupal_get_js() here, in order to have new files added

  // during this request to be loaded by the page. We only want to send back

  // files that the page hasn't already loaded, so we implement simple diffing

  // logic using array_diff_key().

  foreach (array('css', 'js') as $type) {

    // It is highly suspicious if $_POST['ajax_page_state'][$type] is empty,

    // since the base page ought to have at least one JS file and one CSS file

    // loaded. It probably indicates an error, and rather than making the page

    // reload all of the files, instead we return no new files.

    if (empty($_POST['ajax_page_state'][$type])) {

      $items[$type] = array();

    }

    else {

      $function = 'drupal_add_' . $type;

      $items[$type] = $function();

      drupal_alter($type, $items[$type]);

      // @todo Inline CSS and JS items are indexed numerically. These can't be

      //   reliably diffed with array_diff_key(), since the number can change

      //   due to factors unrelated to the inline content, so for now, we strip

      //   the inline items from Ajax responses, and can add support for them

      //   when drupal_add_css() and drupal_add_js() are changed to use a hash

      //   of the inline content as the array key.

      foreach ($items[$type] as $key => $item) {

        if (is_numeric($key)) {

          unset($items[$type][$key]);

        }

      }

      // Ensure that the page doesn't reload what it already has.

      $items[$type] = array_diff_key($items[$type], $_POST['ajax_page_state'][$type]);

    }

  }

  // Render the HTML to load these files, and add AJAX commands to insert this

  // HTML in the page. We pass TRUE as the $skip_alter argument to prevent the

  // data from being altered again, as we already altered it above. Settings are

  // handled separately, afterwards.

  if (isset($items['js']['settings'])) {

    unset($items['js']['settings']);

  }

  $styles = drupal_get_css($items['css'], TRUE);

  $scripts_footer = drupal_get_js('footer', $items['js'], TRUE);

  $scripts_header = drupal_get_js('header', $items['js'], TRUE);

  $extra_commands = array();

  if (!empty($styles)) {

    $extra_commands[] = ajax_command_add_css($styles);

  }

  if (!empty($scripts_header)) {

    $extra_commands[] = ajax_command_prepend('head', $scripts_header);

  }

  if (!empty($scripts_footer)) {

    $extra_commands[] = ajax_command_append('body', $scripts_footer);

  }

  if (!empty($extra_commands)) {

    $commands = array_merge($extra_commands, $commands);

  }

  // Now add a command to merge changes and additions to Drupal.settings.

  $scripts = drupal_add_js();

  drupal_alter('js', $scripts);

  if (!empty($scripts['settings'])) {

    $settings = $scripts['settings'];

    array_unshift($commands, ajax_command_settings(drupal_array_merge_deep_array($settings['data']), TRUE));

  }

  // Allow modules to alter any Ajax response.

  drupal_alter('ajax_render', $commands);

  return drupal_json_encode($commands);

}

/**

 * Gets a form submitted via #ajax during an Ajax callback.

 *

 * This will load a form from the form cache used during Ajax operations. It

 * pulls the form info from $_POST.

 *

 * @return

 *   An array containing the $form, $form_state, $form_id, $form_build_id and an

 *   initial list of Ajax $commands. Use the list() function to break these

 *   apart:

 *   @code

 *     list($form, $form_state, $form_id, $form_build_id, $commands) = ajax_get_form();

 *   @endcode

 */

function ajax_get_form() {

  $form_state = form_state_defaults();

  $form_build_id = $_POST['form_build_id'];

  // Get the form from the cache.

  $form = form_get_cache($form_build_id, $form_state);

  if (!$form) {

    // If $form cannot be loaded from the cache, the form_build_id in $_POST

    // must be invalid, which means that someone performed a POST request onto

    // system/ajax without actually viewing the concerned form in the browser.

    // This is likely a hacking attempt as it never happens under normal

    // circumstances, so we just do nothing.

    watchdog('ajax', 'Invalid form POST data.', array(), WATCHDOG_WARNING);

    drupal_exit();

  }

  // When a page level cache is enabled, the form-build id might have been

  // replaced from within form_get_cache. If this is the case, it is also

  // necessary to update it in the browser by issuing an appropriate Ajax

  // command.

  $commands = array();

  if (isset($form['#build_id_old']) && $form['#build_id_old'] != $form['#build_id']) {

    // If the form build ID has changed, issue an Ajax command to update it.

    $commands[] = ajax_command_update_build_id($form);

    $form_build_id = $form['#build_id'];

  }

  // Since some of the submit handlers are run, redirects need to be disabled.

  $form_state['no_redirect'] = TRUE;

  // When a form is rebuilt after Ajax processing, its #build_id and #action

  // should not change.

  // @see drupal_rebuild_form()

  $form_state['rebuild_info']['copy']['#build_id'] = TRUE;

  $form_state['rebuild_info']['copy']['#action'] = TRUE;

  // The form needs to be processed; prepare for that by setting a few internal

  // variables.

  $form_state['input'] = $_POST;

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

  return array($form, $form_state, $form_id, $form_build_id, $commands);

}

/**

 * Menu callback; handles Ajax requests for the #ajax Form API property.

 *

 * This rebuilds the form from cache and invokes the defined #ajax['callback']

 * to return an Ajax command structure for JavaScript. In case no 'callback' has

 * been defined, nothing will happen.

 *

 * The Form API #ajax property can be set both for buttons and other input

 * elements.

 *

 * This function is also the canonical example of how to implement

 * #ajax['path']. If processing is required that cannot be accomplished with

 * a callback, re-implement this function and set #ajax['path'] to the

 * enhanced function.

 *

 * @see system_menu()

 */

function ajax_form_callback() {

  list($form, $form_state, $form_id, $form_build_id, $commands) = ajax_get_form();

  drupal_process_form($form['#form_id'], $form, $form_state);

  // We need to return the part of the form (or some other content) that needs

  // to be re-rendered so the browser can update the page with changed content.

  // Since this is the generic menu callback used by many Ajax elements, it is

  // up to the #ajax['callback'] function of the element (may or may not be a

  // button) that triggered the Ajax request to determine what needs to be

  // rendered.

  if (!empty($form_state['triggering_element'])) {

    $callback = $form_state['triggering_element']['#ajax']['callback'];

  }

  if (!empty($callback) && is_callable($callback)) {

    $result = $callback($form, $form_state);

    if (!(is_array($result) && isset($result['#type']) && $result['#type'] == 'ajax')) {

      // Turn the response into a #type=ajax array if it isn't one already.

      $result = array(

        '#type' => 'ajax',

        '#commands' => ajax_prepare_response($result),

      );

    }

    $result['#commands'] = array_merge($commands, $result['#commands']);

    return $result;

  }

}

/**

 * Theme callback for Ajax requests.

 *

 * Many different pages can invoke an Ajax request to system/ajax or another

 * generic Ajax path. It is almost always desired for an Ajax response to be

 * rendered using the same theme as the base page, because most themes are built

 * with the assumption that they control the entire page, so if the CSS for two

 * themes are both loaded for a given page, they may conflict with each other.

 * For example, Bartik is Drupal's default theme, and Seven is Drupal's default

 * administration theme. Depending on whether the "Use the administration theme

 * when editing or creating content" checkbox is checked, the node edit form may

 * be displayed in either theme, but the Ajax response to the Field module's

 * "Add another item" button should be rendered using the same theme as the rest

 * of the page. Therefore, system_menu() sets the 'theme callback' for

 * 'system/ajax' to this function, and it is recommended that modules

 * implementing other generic Ajax paths do the same.

 *

 * @see system_menu()

 * @see file_menu()

 */

function ajax_base_page_theme() {

  if (!empty($_POST['ajax_page_state']['theme']) && !empty($_POST['ajax_page_state']['theme_token'])) {

    $theme = $_POST['ajax_page_state']['theme'];

    $token = $_POST['ajax_page_state']['theme_token'];

    // Prevent a request forgery from giving a person access to a theme they

    // shouldn't be otherwise allowed to see. However, since everyone is allowed

    // to see the default theme, token validation isn't required for that, and

    // bypassing it allows most use-cases to work even when accessed from the

    // page cache.

    if ($theme === variable_get('theme_default', 'bartik') || drupal_valid_token($token, $theme)) {

      return $theme;

    }

  }

}

/**

 * Packages and sends the result of a page callback as an Ajax response.

 *

 * This function is the equivalent of drupal_deliver_html_page(), but for Ajax

 * requests. Like that function, it:

 * - Adds needed HTTP headers.

 * - Prints rendered output.

 * - Performs end-of-request tasks.

 *

 * @param $page_callback_result

 *   The result of a page callback. Can be one of:

 *   - NULL: to indicate no content.

 *   - An integer menu status constant: to indicate an error condition.

 *   - A string of HTML content.

 *   - A renderable array of content.

 *

 * @see drupal_deliver_html_page()

 */

function ajax_deliver($page_callback_result) {

  // Browsers do not allow JavaScript to read the contents of a user's local

  // files. To work around that, the jQuery Form plugin submits forms containing

  // a file input element to an IFRAME, instead of using XHR. Browsers do not

  // normally expect JSON strings as content within an IFRAME, so the response

  // must be customized accordingly.

  // @see http://malsup.com/jquery/form/#file-upload

  // @see Drupal.ajax.prototype.beforeSend()

  $iframe_upload = !empty($_POST['ajax_iframe_upload']);

  // Emit a Content-Type HTTP header if none has been added by the page callback

  // or by a wrapping delivery callback.

  if (is_null(drupal_get_http_header('Content-Type'))) {

    if (!$iframe_upload) {

      // Standard JSON can be returned to a browser's XHR object, and to

      // non-browser user agents.

      // @see http://www.ietf.org/rfc/rfc4627.txt?number=4627

      drupal_add_http_header('Content-Type', 'application/json; charset=utf-8');

    }

    else {

      // Browser IFRAMEs expect HTML. With most other content types, Internet

      // Explorer presents the user with a download prompt.

      drupal_add_http_header('Content-Type', 'text/html; charset=utf-8');

    }

  }

  // Let ajax.js know that this response is safe to process.

  ajax_set_verification_header();

  // Print the response.

  $commands = ajax_prepare_response($page_callback_result);

  $json = ajax_render($commands);

  if (!$iframe_upload) {

    // Standard JSON can be returned to a browser's XHR object, and to

    // non-browser user agents.

    print $json;

  }

  else {

    // Browser IFRAMEs expect HTML. Browser extensions, such as Linkification

    // and Skype's Browser Highlighter, convert URLs, phone numbers, etc. into

    // links. This corrupts the JSON response. Protect the integrity of the

    // JSON data by making it the value of a textarea.

    // @see http://malsup.com/jquery/form/#file-upload

    // @see http://drupal.org/node/1009382

    print '<textarea>' . $json . '</textarea>';

  }

  // Perform end-of-request tasks.

  ajax_footer();

}

/**

 * Converts the return value of a page callback into an Ajax commands array.

 *

 * @param $page_callback_result

 *   The result of a page callback. Can be one of:

 *   - NULL: to indicate no content.

 *   - An integer menu status constant: to indicate an error condition.

 *   - A string of HTML content.

 *   - A renderable array of content.

 *

 * @return

 *   An Ajax commands array that can be passed to ajax_render().

 */

function ajax_prepare_response($page_callback_result) {

  $commands = array();

  if (!isset($page_callback_result)) {

    // Simply delivering an empty commands array is sufficient. This results

    // in the Ajax request being completed, but nothing being done to the page.

  }

  elseif (is_int($page_callback_result)) {

    switch ($page_callback_result) {

      case MENU_NOT_FOUND:

        $commands[] = ajax_command_alert(t('The requested page could not be found.'));

        break;

      case MENU_ACCESS_DENIED:

        $commands[] = ajax_command_alert(t('You are not authorized to access this page.'));

        break;

      case MENU_SITE_OFFLINE:

        $commands[] = ajax_command_alert(filter_xss_admin(variable_get('maintenance_mode_message',

          t('@site is currently under maintenance. We should be back shortly. Thank you for your patience.', array('@site' => variable_get('site_name', 'Drupal'))))));

        break;

    }

  }

  elseif (is_array($page_callback_result) && isset($page_callback_result['#type']) && ($page_callback_result['#type'] == 'ajax')) {

    // Complex Ajax callbacks can return a result that contains an error message

    // or a specific set of commands to send to the browser.

    $page_callback_result += element_info('ajax');

    $error = $page_callback_result['#error'];

    if (isset($error) && $error !== FALSE) {

      if ((empty($error) || $error === TRUE)) {

        $error = t('An error occurred while handling the request: The server received invalid input.');

      }

      $commands[] = ajax_command_alert($error);

    }

    else {

      $commands = $page_callback_result['#commands'];

    }

  }

  else {

    // Like normal page callbacks, simple Ajax callbacks can return HTML

    // content, as a string or render array. This HTML is inserted in some

    // relationship to #ajax['wrapper'], as determined by which jQuery DOM

    // manipulation method is used. The method used is specified by

    // #ajax['method']. The default method is 'replaceWith', which completely

    // replaces the old wrapper element and its content with the new HTML.

    $html = is_string($page_callback_result) ? $page_callback_result : drupal_render($page_callback_result);

    $commands[] = ajax_command_insert(NULL, $html);

    // Add the status messages inside the new content's wrapper element, so that

    // on subsequent Ajax requests, it is treated as old content.

    $commands[] = ajax_command_prepend(NULL, theme('status_messages'));

  }

  return $commands;

}

/**

 * Sets a response header for ajax.js to trust the response body.

 *

 * It is not safe to invoke Ajax commands within user-uploaded files, so this

 * header protects against those being invoked.

 *

 * @see Drupal.ajax.options.success()

 */

function ajax_set_verification_header() {

  $added = &drupal_static(__FUNCTION__);

  // User-uploaded files cannot set any response headers, so a custom header is

  // used to indicate to ajax.js that this response is safe. Note that most

  // Ajax requests bound using the Form API will be protected by having the URL

  // flagged as trusted in Drupal.settings, so this header is used only for

  // things like custom markup that gets Ajax behaviors attached.

  if (empty($added)) {

    drupal_add_http_header('X-Drupal-Ajax-Token', '1');

    // Avoid sending the header twice.

    $added = TRUE;

  }

}

/**

 * Performs end-of-Ajax-request tasks.

 *

 * This function is the equivalent of drupal_page_footer(), but for Ajax

 * requests.

 *

 * @see drupal_page_footer()

 */

function ajax_footer() {

  // Even for Ajax requests, invoke hook_exit() implementations. There may be

  // modules that need very fast Ajax responses, and therefore, run Ajax

  // requests with an early bootstrap.

  if (drupal_get_bootstrap_phase() == DRUPAL_BOOTSTRAP_FULL && (!defined('MAINTENANCE_MODE') || MAINTENANCE_MODE != 'update')) {

    module_invoke_all('exit');

  }

  // Commit the user session. See above comment about the possibility of this

  // function running without session.inc loaded.

  if (function_exists('drupal_session_commit')) {

    drupal_session_commit();

  }

}

/**

 * Form element processing handler for the #ajax form property.

 *

 * @param $element

 *   An associative array containing the properties of the element.

 *

 * @return

 *   The processed element.

 *

 * @see ajax_pre_render_element()

 */

function ajax_process_form($element, &$form_state) {

  $element = ajax_pre_render_element($element);

  if (!empty($element['#ajax_processed'])) {

    $form_state['cache'] = TRUE;

  }

  return $element;

}

/**

 * Adds Ajax information about an element to communicate with JavaScript.

 *

 * If #ajax['path'] is set on an element, this additional JavaScript is added

 * to the page header to attach the Ajax behaviors. See ajax.js for more

 * information.

 *

 * @param $element

 *   An associative array containing the properties of the element.

 *   Properties used:

 *   - #ajax['event']

 *   - #ajax['prevent']

 *   - #ajax['path']

 *   - #ajax['options']

 *   - #ajax['wrapper']

 *   - #ajax['parameters']

 *   - #ajax['effect']

 *

 * @return

 *   The processed element with the necessary JavaScript attached to it.

 */

function ajax_pre_render_element($element) {

  // Skip already processed elements.

  if (isset($element['#ajax_processed'])) {

    return $element;

  }

  // Initialize #ajax_processed, so we do not process this element again.

  $element['#ajax_processed'] = FALSE;

  // Nothing to do if there is neither a callback nor a path.

  if (!(isset($element['#ajax']['callback']) || isset($element['#ajax']['path']))) {

    return $element;

  }

  // Add a reasonable default event handler if none was specified.

  if (isset($element['#ajax']) && !isset($element['#ajax']['event'])) {

    switch ($element['#type']) {

      case 'submit':

      case 'button':

      case 'image_button':

        // Pressing the ENTER key within a textfield triggers the click event of

        // the form's first submit button. Triggering Ajax in this situation

        // leads to problems, like breaking autocomplete textfields, so we bind

        // to mousedown instead of click.

        // @see http://drupal.org/node/216059

        $element['#ajax']['event'] = 'mousedown';

        // Retain keyboard accessibility by setting 'keypress'. This causes

        // ajax.js to trigger 'event' when SPACE or ENTER are pressed while the

        // button has focus.

        $element['#ajax']['keypress'] = TRUE;

        // Binding to mousedown rather than click means that it is possible to

        // trigger a click by pressing the mouse, holding the mouse button down

        // until the Ajax request is complete and the button is re-enabled, and

        // then releasing the mouse button. Set 'prevent' so that ajax.js binds

        // an additional handler to prevent such a click from triggering a

        // non-Ajax form submission. This also prevents a textfield's ENTER

        // press triggering this button's non-Ajax form submission behavior.

        if (!isset($element['#ajax']['prevent'])) {

          $element['#ajax']['prevent'] = 'click';

        }

        break;

      case 'password':

      case 'textfield':

      case 'textarea':

        $element['#ajax']['event'] = 'blur';

        break;

      case 'radio':

      case 'checkbox':

      case 'select':

        $element['#ajax']['event'] = 'change';

        break;

      case 'link':

        $element['#ajax']['event'] = 'click';

        break;

      default:

        return $element;

    }

  }

  // Attach JavaScript settings to the element.

  if (isset($element['#ajax']['event'])) {

    $element['#attached']['library'][] = array('system', 'jquery.form');

    $element['#attached']['library'][] = array('system', 'drupal.ajax');

    $settings = $element['#ajax'];

    // Assign default settings.

    $settings += array(

      'path' => 'system/ajax',

      'options' => array(),

    );

    // @todo Legacy support. Remove in Drupal 8.

    if (isset($settings['method']) && $settings['method'] == 'replace') {

      $settings['method'] = 'replaceWith';

    }

    // Change path to URL.

    $settings['url'] = url($settings['path'], $settings['options']);

    unset($settings['path'], $settings['options']);

    // Add special data to $settings['submit'] so that when this element

    // triggers an Ajax submission, Drupal's form processing can determine which

    // element triggered it.

    // @see _form_element_triggered_scripted_submission()

    if (isset($settings['trigger_as'])) {

      // An element can add a 'trigger_as' key within #ajax to make the element

      // submit as though another one (for example, a non-button can use this

      // to submit the form as though a button were clicked). When using this,

      // the 'name' key is always required to identify the element to trigger

      // as. The 'value' key is optional, and only needed when multiple elements

      // share the same name, which is commonly the case for buttons.

      $settings['submit']['_triggering_element_name'] = $settings['trigger_as']['name'];

      if (isset($settings['trigger_as']['value'])) {

        $settings['submit']['_triggering_element_value'] = $settings['trigger_as']['value'];

      }

      unset($settings['trigger_as']);

    }

    elseif (isset($element['#name'])) {

      // Most of the time, elements can submit as themselves, in which case the

      // 'trigger_as' key isn't needed, and the element's name is used.

      $settings['submit']['_triggering_element_name'] = $element['#name'];

      // If the element is a (non-image) button, its name may not identify it

      // uniquely, in which case a match on value is also needed.

      // @see _form_button_was_clicked()

      if (isset($element['#button_type']) && empty($element['#has_garbage_value'])) {

        $settings['submit']['_triggering_element_value'] = $element['#value'];

      }

    }

    // Convert a simple #ajax['progress'] string into an array.

    if (isset($settings['progress']) && is_string($settings['progress'])) {

      $settings['progress'] = array('type' => $settings['progress']);

    }

    // Change progress path to a full URL.

    if (isset($settings['progress']['path'])) {

      $settings['progress']['url'] = url($settings['progress']['path']);

      unset($settings['progress']['path']);

    }

    $element['#attached']['js'][] = array(

      'type' => 'setting',

      'data' => array(

        'ajax' => array($element['#id'] => $settings),

        'urlIsAjaxTrusted' => array(

          $settings['url'] => TRUE,

        ),

      ),

    );

    // Indicate that Ajax processing was successful.

    $element['#ajax_processed'] = TRUE;

  }

  return $element;

}

/**

 * @} End of "defgroup ajax".

 */

/**

 * @defgroup ajax_commands Ajax framework commands

 * @{

 * Functions to create various Ajax commands.

 *

 * These functions can be used to create arrays for use with the

 * ajax_render() function.

 */

/**

 * Creates a Drupal Ajax 'alert' command.

 *

 * The 'alert' command instructs the client to display a JavaScript alert

 * dialog box.

 *

 * This command is implemented by Drupal.ajax.prototype.commands.alert()

 * defined in misc/ajax.js.

 *

 * @param $text

 *   The message string to display to the user.

 *

 * @return

 *   An array suitable for use with the ajax_render() function.

 */

function ajax_command_alert($text) {

  return array(

    'command' => 'alert',

    'text' => $text,

  );

}

/**

 * Creates a Drupal Ajax 'insert' command using the method in #ajax['method'].

 *

 * This command instructs the client to insert the given HTML using whichever

 * jQuery DOM manipulation method has been specified in the #ajax['method']

 * variable of the element that triggered the request.

 *

 * This command is implemented by Drupal.ajax.prototype.commands.insert()

 * defined in misc/ajax.js.

 *

 * @param $selector

 *   A jQuery selector string. If the command is a response to a request from

 *   an #ajax form element then this value can be NULL.

 * @param $html

 *   The data to use with the jQuery method.

 * @param $settings

 *   An optional array of settings that will be used for this command only.

 *

 * @return

 *   An array suitable for use with the ajax_render() function.

 */

function ajax_command_insert($selector, $html, $settings = NULL) {

  return array(

    'command' => 'insert',

    'method' => NULL,

    'selector' => $selector,

    'data' => $html,

    'settings' => $settings,

  );

}

/**

 * Creates a Drupal Ajax 'insert/replaceWith' command.

 *

 * The 'insert/replaceWith' command instructs the client to use jQuery's

 * replaceWith() method to replace each element matched matched by the given

 * selector with the given HTML.

 *

 * This command is implemented by Drupal.ajax.prototype.commands.insert()

 * defined in misc/ajax.js.

 *

 * @param $selector

 *   A jQuery selector string. If the command is a response to a request from

 *   an #ajax form element then this value can be NULL.

 * @param $html

 *   The data to use with the jQuery replaceWith() method.

 * @param $settings

 *   An optional array of settings that will be used for this command only.

 *

 * @return

 *   An array suitable for use with the ajax_render() function.

 *

 * See

 * @link http://docs.jquery.com/Manipulation/replaceWith#content jQuery replaceWith command @endlink

 */

function ajax_command_replace($selector, $html, $settings = NULL) {

  return array(

    'command' => 'insert',

    'method' => 'replaceWith',

    'selector' => $selector,

    'data' => $html,

    'settings' => $settings,

  );

}

/**

 * Creates a Drupal Ajax 'insert/html' command.

 *

 * The 'insert/html' command instructs the client to use jQuery's html()

 * method to set the HTML content of each element matched by the given

 * selector while leaving the outer tags intact.

 *

 * This command is implemented by Drupal.ajax.prototype.commands.insert()

 * defined in misc/ajax.js.

 *

 * @param $selector

 *   A jQuery selector string. If the command is a response to a request from

 *   an #ajax form element then this value can be NULL.

 * @param $html

 *   The data to use with the jQuery html() method.

 * @param $settings

 *   An optional array of settings that will be used for this command only.

 *

 * @return

 *   An array suitable for use with the ajax_render() function.

 *

 * @see http://docs.jquery.com/Attributes/html#val

 */

function ajax_command_html($selector, $html, $settings = NULL) {

  return array(

    'command' => 'insert',

    'method' => 'html',

    'selector' => $selector,

    'data' => $html,

    'settings' => $settings,

  );

}

/**

 * Creates a Drupal Ajax 'insert/prepend' command.

 *

 * The 'insert/prepend' command instructs the client to use jQuery's prepend()

 * method to prepend the given HTML content to the inside each element matched

 * by the given selector.

 *

 * This command is implemented by Drupal.ajax.prototype.commands.insert()

 * defined in misc/ajax.js.

 *

 * @param $selector

 *   A jQuery selector string. If the command is a response to a request from

 *   an #ajax form element then this value can be NULL.

 * @param $html

 *   The data to use with the jQuery prepend() method.

 * @param $settings

 *   An optional array of settings that will be used for this command only.

 *

 * @return

 *   An array suitable for use with the ajax_render() function.

 *

 * @see http://docs.jquery.com/Manipulation/prepend#content

 */

function ajax_command_prepend($selector, $html, $settings = NULL) {

  return array(

    'command' => 'insert',

    'method' => 'prepend',

    'selector' => $selector,

    'data' => $html,

    'settings' => $settings,

  );

}

/**

 * Creates a Drupal Ajax 'insert/append' command.

 *

 * The 'insert/append' command instructs the client to use jQuery's append()

 * method to append the given HTML content to the inside of each element matched

 * by the given selector.

 *

 * This command is implemented by Drupal.ajax.prototype.commands.insert()

 * defined in misc/ajax.js.

 *

 * @param $selector

 *   A jQuery selector string. If the command is a response to a request from

 *   an #ajax form element then this value can be NULL.

 * @param $html

 *   The data to use with the jQuery append() method.

 * @param $settings

 *   An optional array of settings that will be used for this command only.

 *

 * @return

 *   An array suitable for use with the ajax_render() function.

 *

 * @see http://docs.jquery.com/Manipulation/append#content

 */

function ajax_command_append($selector, $html, $settings = NULL) {

  return array(

    'command' => 'insert',

    'method' => 'append',

    'selector' => $selector,

    'data' => $html,

    'settings' => $settings,

  );

}

/**

 * Creates a Drupal Ajax 'insert/after' command.

 *

 * The 'insert/after' command instructs the client to use jQuery's after()

 * method to insert the given HTML content after each element matched by

 * the given selector.

 *

 * This command is implemented by Drupal.ajax.prototype.commands.insert()

 * defined in misc/ajax.js.

 *

 * @param $selector

 *   A jQuery selector string. If the command is a response to a request from

 *   an #ajax form element then this value can be NULL.

 * @param $html

 *   The data to use with the jQuery after() method.

 * @param $settings

 *   An optional array of settings that will be used for this command only.

 *

 * @return

 *   An array suitable for use with the ajax_render() function.

 *

 * @see http://docs.jquery.com/Manipulation/after#content

 */

function ajax_command_after($selector, $html, $settings = NULL) {

  return array(

    'command' => 'insert',

    'method' => 'after',

    'selector' => $selector,

    'data' => $html,

    'settings' => $settings,

  );

}

/**

 * Creates a Drupal Ajax 'insert/before' command.

 *

 * The 'insert/before' command instructs the client to use jQuery's before()

 * method to insert the given HTML content before each of elements matched by

 * the given selector.

 *

 * This command is implemented by Drupal.ajax.prototype.commands.insert()

 * defined in misc/ajax.js.

 *

 * @param $selector

 *   A jQuery selector string. If the command is a response to a request from

 *   an #ajax form element then this value can be NULL.

 * @param $html

 *   The data to use with the jQuery before() method.

 * @param $settings

 *   An optional array of settings that will be used for this command only.

 *

 * @return

 *   An array suitable for use with the ajax_render() function.

 *

 * @see http://docs.jquery.com/Manipulation/before#content

 */

function ajax_command_before($selector, $html, $settings = NULL) {

  return array(

    'command' => 'insert',

    'method' => 'before',

    'selector' => $selector,

    'data' => $html,

    'settings' => $settings,

  );

}

/**

 * Creates a Drupal Ajax 'remove' command.

 *

 * The 'remove' command instructs the client to use jQuery's remove() method

 * to remove each of elements matched by the given selector, and everything

 * within them.

 *

 * This command is implemented by Drupal.ajax.prototype.commands.remove()

 * defined in misc/ajax.js.

 *

 * @param $selector

 *   A jQuery selector string. If the command is a response to a request from

 *   an #ajax form element then this value can be NULL.

 *

 * @return

 *   An array suitable for use with the ajax_render() function.

 *

 * @see http://docs.jquery.com/Manipulation/remove#expr

 */

function ajax_command_remove($selector) {

  return array(

    'command' => 'remove',

    'selector' => $selector,

  );

}

/**

 * Creates a Drupal Ajax 'changed' command.

 *

 * This command instructs the client to mark each of the elements matched by the

 * given selector as 'ajax-changed'.

 *

 * This command is implemented by Drupal.ajax.prototype.commands.changed()

 * defined in misc/ajax.js.

 *

 * @param $selector

 *   A jQuery selector string. If the command is a response to a request from

 *   an #ajax form element then this value can be NULL.

 * @param $asterisk

 *   An optional CSS selector which must be inside $selector. If specified,

 *   an asterisk will be appended to the HTML inside the $asterisk selector.

 *

 * @return

 *   An array suitable for use with the ajax_render() function.

 */

function ajax_command_changed($selector, $asterisk = '') {

  return array(

    'command' => 'changed',

    'selector' => $selector,

    'asterisk' => $asterisk,

  );

}

/**

 * Creates a Drupal Ajax 'css' command.

 *

 * The 'css' command will instruct the client to use the jQuery css() method

 * to apply the CSS arguments to elements matched by the given selector.

 *

 * This command is implemented by Drupal.ajax.prototype.commands.css()

 * defined in misc/ajax.js.

 *

 * @param $selector

 *   A jQuery selector string. If the command is a response to a request from

 *   an #ajax form element then this value can be NULL.

 * @param $argument

 *   An array of key/value pairs to set in the CSS for the selector.

 *

 * @return

 *   An array suitable for use with the ajax_render() function.

 *

 * @see http://docs.jquery.com/CSS/css#properties

 */

function ajax_command_css($selector, $argument) {

  return array(

    'command' => 'css',

    'selector' => $selector,

    'argument' => $argument,

  );

}

/**

 * Creates a Drupal Ajax 'settings' command.

 *

 * The 'settings' command instructs the client either to use the given array as

 * the settings for ajax-loaded content or to extend Drupal.settings with the

 * given array, depending on the value of the $merge parameter.

 *

 * This command is implemented by Drupal.ajax.prototype.commands.settings()

 * defined in misc/ajax.js.

 *

 * @param $argument

 *   An array of key/value pairs to add to the settings. This will be utilized

 *   for all commands after this if they do not include their own settings

 *   array.

 * @param $merge

 *   Whether or not the passed settings in $argument should be merged into the

 *   global Drupal.settings on the page. By default (FALSE), the settings that

 *   are passed to Drupal.attachBehaviors will not include the global

 *   Drupal.settings.

 *

 * @return

 *   An array suitable for use with the ajax_render() function.

 */

function ajax_command_settings($argument, $merge = FALSE) {

  return array(

    'command' => 'settings',

    'settings' => $argument,

    'merge' => $merge,

  );

}

/**

 * Creates a Drupal Ajax 'data' command.

 *

 * The 'data' command instructs the client to attach the name=value pair of

 * data to the selector via jQuery's data cache.

 *

 * This command is implemented by Drupal.ajax.prototype.commands.data()

 * defined in misc/ajax.js.

 *

 * @param $selector

 *   A jQuery selector string. If the command is a response to a request from

 *   an #ajax form element then this value can be NULL.

 * @param $name

 *   The name or key (in the key value pair) of the data attached to this

 *   selector.

 * @param $value

 *   The value of the data. Not just limited to strings can be any format.

 *

 * @return

 *   An array suitable for use with the ajax_render() function.

 *

 * @see http://docs.jquery.com/Core/data#namevalue

 */

function ajax_command_data($selector, $name, $value) {

  return array(

    'command' => 'data',

    'selector' => $selector,

    'name' => $name,

    'value' => $value,

  );

}

/**

 * Creates a Drupal Ajax 'invoke' command.

 *

 * The 'invoke' command will instruct the client to invoke the given jQuery

 * method with the supplied arguments on the elements matched by the given

 * selector. Intended for simple jQuery commands, such as attr(), addClass(),

 * removeClass(), toggleClass(), etc.

 *

 * This command is implemented by Drupal.ajax.prototype.commands.invoke()

 * defined in misc/ajax.js.

 *

 * @param $selector

 *   A jQuery selector string. If the command is a response to a request from

 *   an #ajax form element then this value can be NULL.

 * @param $method

 *   The jQuery method to invoke.

 * @param $arguments

 *   (optional) A list of arguments to the jQuery $method, if any.

 *

 * @return

 *   An array suitable for use with the ajax_render() function.

 */

function ajax_command_invoke($selector, $method, array $arguments = array()) {

  return array(

    'command' => 'invoke',

    'selector' => $selector,

    'method' => $method,

    'arguments' => $arguments,

  );

}

/**

 * Creates a Drupal Ajax 'restripe' command.

 *

 * The 'restripe' command instructs the client to restripe a table. This is

 * usually used after a table has been modified by a replace or append command.

 *

 * This command is implemented by Drupal.ajax.prototype.commands.restripe()

 * defined in misc/ajax.js.

 *

 * @param $selector

 *   A jQuery selector string.

 *

 * @return

 *   An array suitable for use with the ajax_render() function.

 */

function ajax_command_restripe($selector) {

  return array(

    'command' => 'restripe',

    'selector' => $selector,

  );

}

/**

 * Creates a Drupal Ajax 'update_build_id' command.

 *

 * This command updates the value of a hidden form_build_id input element on a

 * form. It requires the form passed in to have keys for both the old build ID

 * in #build_id_old and the new build ID in #build_id.

 *

 * The primary use case for this Ajax command is to serve a new build ID to a

 * form served from the cache to an anonymous user, preventing one anonymous

 * user from accessing the form state of another anonymous users on Ajax enabled

 * forms.

 *

 * @param $form

 *   The form array representing the form whose build ID should be updated.

 */

function ajax_command_update_build_id($form) {

  return array(

    'command' => 'updateBuildId',

    'old' => $form['#build_id_old'],

    'new' => $form['#build_id'],

  );

}

/**

 * Creates a Drupal Ajax 'add_css' command.

 *

 * This method will add css via ajax in a cross-browser compatible way.

 *

 * This command is implemented by Drupal.ajax.prototype.commands.add_css()

 * defined in misc/ajax.js.

 *

 * @param $styles

 *   A string that contains the styles to be added.

 *

 * @return

 *   An array suitable for use with the ajax_render() function.

 *

 * @see misc/ajax.js

 */

function ajax_command_add_css($styles) {

  return array(

    'command' => 'add_css',

    'data' => $styles,

  );

}