/**
  * @param string $id Form identifier
  * @param HttpUrl $action form action (url to which it will be sumbitted)
  * @param string $sign form signature to protect it from vulnerabilities;
  */
 function __construct($id, HttpUrl $action, $sign)
 {
     $this->signer = new XorCipherer($sign);
     parent::__construct($id, $action, RequestMethod::post());
 }