_ajax.php

<?php

$data = new stdClass();

if (isset($_SERVER['HTTP_X_REQUESTED_WITH'])) {
	if ($_SERVER['REQUEST_METHOD'] == 'POST') {
		/* Router */
		if (isset($_POST['buy'])) {
			$data->success = TRUE;
			$data->message = 'Message succesfully sent';
		}
		/* /Router */
	} else {
		$data->success = FALSE;
		$data->message = 'Error occurred! Method "'. $_SERVER['REQUEST_METHOD'] .'" not allowed.';
		header('Status: 405 Method Not Allowed');
	}
} else {
	$data->success = FALSE;
	$data->message = 'Error occurred! Only AJAX requests allowed.';
	header('Status: 400 Bad Request');
}

print json_encode($data); die;