wp-fast-ajax-shortinit-simple.php

<?php
// File: ajax.php (Root WP Install)

// Init
// -----------------------------------------------------------------------
define('DOING_AJAX', true);
define('SHORTINIT', true);

// WP Load
// -----------------------------------------------------------------------
require('wp-load.php');
$ajax_actions = '/includes/ajax-actions.php';

// Ajax Check
// -----------------------------------------------------------------------
@header('X-Robots-Tag: noindex');
send_nosniff_header();
nocache_headers();

if(empty($_REQUEST['action']))
    wp_die('0', 400);

// Ajax Requirements & Actions
// -----------------------------------------------------------------------
require(ABSPATH . WPINC . '/theme.php');
require(get_stylesheet_directory() . $ajax_actions);

// Ajax Apply Hooks
// -----------------------------------------------------------------------
if(!has_action('wp_ajax_' . $_REQUEST['action']))
    wp_die('0', 400);

do_action('wp_ajax_' . $_REQUEST['action']);

wp_die('0');