Does the functions.php file ever get called during an AJAX call? Debug AJAX

2 comments

1. admin-ajax.php loads wp-load.php:

   /** Load WordPress Bootstrap */
   require_once( dirname( dirname( __FILE__ ) ) . '/wp-load.php' );
   

   wp-load.php loads wp-config.php, and there wp-settings.php is loaded.

   And here we find this:

   // Load the functions for the active theme, for both parent and child theme if applicable.
   if ( ! defined( 'WP_INSTALLING' ) || 'wp-activate.php' === $pagenow ) {
       if ( TEMPLATEPATH !== STYLESHEETPATH && file_exists( STYLESHEETPATH . '/functions.php' ) )
           include( STYLESHEETPATH . '/functions.php' );
       if ( file_exists( TEMPLATEPATH . '/functions.php' ) )
           include( TEMPLATEPATH . '/functions.php' );
   }
   

   So, yes, the theme’s functions.php is loaded.

   ---

   There is one exception in wp-settings.php:

   // Stop most of WordPress from being loaded if we just want the basics.
   if ( SHORTINIT )
       return false;
   

   When SHORTINIT is defined as TRUE earlier, the theme will not be loaded.

   So check if SHORTINIT is TRUE for some reason.

   ---

   Another common error is the wrong usage of is_admin(). This is always TRUE in admin-ajax.php, so the following will fail:

   if ( ! is_admin() )
       // register or execute AJAX stuff
   

   ---

   Debugging AJAX

   One method as primitive as efficient is using HTTP header to debug AJAX.

   Here is a simple helper function:

   function send_debug_header( $msg )
   {
       static $counter = 1;
       header( "X-Debug-Ajax-$counter: $msg" );
       $counter += 1;
   }
   

   And this plugin shows how to use it:

   <?php # -*- coding: utf-8 -*-
   /**
    * Plugin Name: Debug AJAX per HTTP
    * Description: Look at the HTTP headers in your browser's network console
    */
   
   // The constant is already defined when plugins are loaded.
   // Prove we have been called.
   if ( defined( 'DOING_AJAX' ) && DOING_AJAX )
       send_debug_header( 'File "' . __FILE__ . '" was called on an AJAX request.' );
   
   function send_debug_header( $msg )
   {
       static $counter = 1;
       header( "X-Debug-Ajax-$counter: $msg" );
       $counter += 1;
   }
   
   add_action( 'wp_ajax_debug_test',        't5_debug_test' );
   add_action( 'wp_ajax_nopriv_debug_test', 't5_debug_test' );
   
   function t5_debug_test()
   {
       $in = is_user_logged_in() ? '' : 'not ';
       send_debug_header( 'Function "' . __FUNCTION__ . '" was called and the user is ' . $in . 'logged in.' );
       print_r( debug_backtrace() );
       die(1);
   }
   
   add_action( 'wp_enqueue_scripts', 't5_enqueue_jquery' );
   
   function t5_enqueue_jquery()
   {
       wp_enqueue_script( 'jquery' );
   }
   add_action( 'wp_footer', 't5_debug_ajax_test_button', 0 );
   
   function t5_debug_ajax_test_button()
   {
       ?>
   <input type="submit" id="t5debugajax" value="Debug AJAX">
   <script>
   jQuery( function($){
       var sendFeedBack = function( response ){
           console.log( response );
       };
       $("#t5debugajax").on("click", function(){
           $.post(
               "<?php echo admin_url( 'admin-ajax.php' ); ?>",
               {
                   action: "debug_test"
               },
               sendFeedBack
           );
       });
   });
   </script>
       <?php
   }
   

   It will add a button to the front end that triggers an AJAX request when clicked. The open your browser’s network console and look at the response headers for the request:

   

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2. I assume your problem AJAX was working if your are logged in and it was not working in logged out status, right?
   There is a function in WordPress to access AJAX-based files for non logged users: wp_ajax_nopriv, for example

   /* works for logged users */
   add_action( 'wp_ajax_my_action', 'my_action_callback');
   
   /* works for non logged users */
   add_action( 'wp_ajax_nopriv_my_action', 'my_action_callback');
   

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