Ajax request - access only from local domain

How make this code in phalcon?

$domain = parse_url($_SERVER['HTTP_REFERER']);\n
$domain = $domain['host'];
if($domain != $_SERVER['SERVER_NAME'])
    die();

I want to Ajax requests were only available with the local domain...but code not work:

class AjaxController extends AjaxResponse
{
    public function initialize()
    {
        $request = new Phalcon\Http\Request();
        $host = $request->getHttpHost();
        // return string(10) "localhost3"

        $referer = $request->getHTTPReferer();
        // return string(0) ""

        die(var_dump($referer));
    }

    public function indexAction()
    {
        $this->view->disable();
        die("0");
    }

    public function authenticationAction() 
    {
        $this->setJsonResponse();
        return array("ajax" => false, "details" => "test" );
    }

    public function dAction() 
    {
        $this->setJsonResponse();
        return array("ajax" => false, "details" => "test" );
    }
}

Maybe there are other ways to improve the security of ajax requests?