1 ajax.inc ajax_deliver($page_callback_result)

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

This function is the equivalent of backdrop_deliver_html_page(), but for Ajax requests. Like that function, it:

  • Adds needed HTTP headers.
  • Prints rendered output.
  • Performs end-of-request tasks.


$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 also


Related topics


core/includes/ajax.inc, line 477
Functions for use with Backdrop's Ajax framework.


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 Backdrop.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(backdrop_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
      backdrop_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.
      backdrop_add_http_header('Content-Type', 'text/html; charset=utf-8');

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

  // 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.