How to make custom button link on the WordPress Admin Bar run by AJAX

Question

I know how to add a link in the admin bar using admin_bar_menu action. I want to run a script to purge cache on a click of button present in admin bar by AJAX.

function add_item($admin_bar){
    global $pagenow;
    $admin_bar->add_menu(array('id'=>'cache-purge','title'=>'Cache Purge','href'=>'http://example.com/purge'));
}
add_action('admin_bar_menu', 'add_item', 100);

Is there any way to run that link without going over to that but by AJAX?

Answer 1

Below is the complete code on how to do it. For more details you may like to see how admin ajax work on codex.

<?php

/* Your code to add menu on admin bar */

add_action('admin_bar_menu', 'add_item', 100);

function add_item( $admin_bar ){
  global $pagenow;
  $admin_bar->add_menu( array( 'id'=>'cache-purge','title'=>'Cache Purge','href'=>'#' ) );
}

/* Here you trigger the ajax handler function using jQuery */

add_action( 'admin_footer', 'cache_purge_action_js' );

function cache_purge_action_js() { ?>
  <script type="text/javascript" >
     jQuery("li#wp-admin-bar-cache-purge .ab-item").on( "click", function() {
        var data = {
                      'action': 'example_cache_purge',
                    };

        /* since 2.8 ajaxurl is always defined in the admin header and points to admin-ajax.php */
        jQuery.post(ajaxurl, data, function(response) {
           alert( response );
        });

      });
  </script> <?php
}

/* Here you hook and define ajax handler function */

add_action( 'wp_ajax_example_cache_purge', 'example_cache_purge_callback' );

function example_cache_purge_callback() {
    global $wpdb; /* this is how you get access to the database */
    /* You cache purge logic should go here. */
    $response = "Cache Purged !";
    echo $response;
    wp_die(); /* this is required to terminate immediately and return a proper     response */
} 
?>