Copy the below code in a file (frontend-ajax.php) and call it as an AJAX url.
PHP code:
define("DOING_AJAX", true);
require_once("../../../wp-load.php"); // Add wp-load.php file.
if(!isset($_REQUEST["action"]) || trim($_REQUEST["action"])==""){
die("-1");
}
@header("Content-Type: text/html; charset=".get_option("blog_charset"));
require_once("../../../wp-load.php"); // Add wp-load.php file.
if(!isset($_REQUEST["action"]) || trim($_REQUEST["action"])==""){
die("-1");
}
@header("Content-Type: text/html; charset=".get_option("blog_charset"));
include_once("filePath"); // Including your plugin’s main file where ajax actions are defined.
send_nosniff_header();
if(has_action("wp_ajax_".$_REQUEST["action"])){
do_action("wp_ajax_".$_REQUEST["action"]);
exit;
}
status_header(404);