Frontend AJAX in WordPress

wp-fronted_ajax.php

<?php
//Frontend AJAX in WordPress //http://codex.wordpress.org/AJAX_in_Plugins
define('DOING_AJAX', true);
/* Assuming you will put this file in your plugin's directory */
require_once(dirname(__FILE__).DIRECTORY_SEPARATOR.'..'.DIRECTORY_SEPARATOR.'..'.DIRECTORY_SEPARATOR.'..'.DIRECTORY_SEPARATOR.'wp-load.php');
if(!isset($_REQUEST['action']) || trim($_REQUEST['action'])=='')
{
    die('-1');
}
@header('Content-Type: text/html; charset='.get_option('blog_charset'));
/* Including your plugin's main file where ajax actions are defined */
include_once(dirname(__FILE__).DIRECTORY_SEPARATOR.'main-plugin-file.php');
send_nosniff_header();
if(has_action('wp_ajax_'.$_REQUEST['action']))
{
    do_action('wp_ajax_'.$_REQUEST['action']);
    exit;
}
status_header(404);
?>