I'm currently developing a plugin that uses ajax functionality.

Problem: The callback isn't fired = no data gets processed.

if ( ! is_admin() )
    add_action( 'after_setup_theme', array( 'wpseAjaxClass', 'init' ), 10 );
  • Last time I had this issue was due to the callback function not actually being accessible during the AJAX request. For example, I buried the call to instantiate the class under a function like is_single(). It was called when the page was being viewed, but not when the AJAX request was made. I see that one of your comments says the code is part of the class. Any chance you can show the rest of the class?
    – tollmanz
    Commented Feb 6, 2012 at 5:17
  • @tollmanz Thanks for the comment. jQuery mobile loads everything with one request, so basically it's like a js-slider/-carousel. The my_action_cb() fn itself isn't hidden behind something. Just sits right in the middle of the class. As shown in the, the enqueue happens right in the __construct() of the class. I added a screenshot from the console. Please see Edit. Any other ideas?
    – kaiser
    Commented Feb 6, 2012 at 5:44
  • Sorry to harp on this, but clearly the script cannot find the function. How is the class itself instantiated? When I have these issues, it's usually something little that I've missed. I'd love to look over the code to see if I could spot something.
    – tollmanz
    Commented Feb 6, 2012 at 5:58
  • Ok :) Here's a pastebin. Tell me if the link isn't working. (And thanks for taking the time).
    – kaiser
    Commented Feb 6, 2012 at 6:00
  • 1
    To be more clear, I created this revised pastebin based on your pastebin: pastebin.com/r0Ud14aB
    – tollmanz
    Commented Feb 6, 2012 at 6:11

1 Answer 1


The answer was as stupid as simple: I wrapped the init for the class in a ! is_admin() call. This successfully prevented the callback from beeing fired.

Rule for AJAX loading

  • Load it in public
  • Don't hide it behind a ! is_admin() call.

The 2nd line from admin-ajax.php

define( 'WP_ADMIN', true );
  • 2
    I knew it was going to be something like this. Whenever I get the dreaded "0" response with WP AJAX, I instantly think that my function is inaccessible! Congrats on finding the issue and getting your life back ;)
    – tollmanz
    Commented Feb 7, 2012 at 3:43
  • :) Thanks for this comment. I'm currently more than angry about this issue and writing on wp-hackers :P
    – kaiser
    Commented Feb 7, 2012 at 3:48
  • Also - don't pass a parameter called "action" inside your ajax callback routine - unless you want to seriously mess your own mind up!
    – Q Studio
    Commented Sep 11, 2017 at 14:40
  • @QStudio mind to clarify in an answer?
    – kaiser
    Commented Sep 11, 2017 at 15:20
  • 1
    @QStudio haha! No worries. Happens to the best!
    – kaiser
    Commented Sep 11, 2017 at 16:36

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