Feb 18, 2016

Using Wordpress AJAX on Frontend

wp_ajax_* callback functions will return 0 if they are called on the frontend by anonymous users.

This is because of security reasons, but Wordpress has prefixes for "unsecure" calls: wp_ajax_nopriv_*.

Both of the hooks need to be defined to work with logged in and anonymous users.

In functions.php define:
add_action( 'wp_ajax_call_stuff', 'my_callback' );
add_action( 'wp_ajax_nopriv_call_stuff', 'my_callback' );
function my_callback() {

Another thing to add is the ajaxurl variable, which is not included on the frontend by default. You can do this in many ways, but I figured the best thing to do is to use wp_localize_script().
wp_localize_script('my_main_script', 'myPrefix', array( 'ajaxurl' => admin_url( 'admin-ajax.php')));

Then, you can call the AJAX request like this:
jQuery.post(myPrefix.ajaxurl, {
  'action': 'call_stuff',
  'whatever': '1'
  alert('The server responded: ' + response);