public function getNotifyResponseStringJson() {
    $response['Result'] = $this->notifyResponse['Result'];
    $response['ErrorMessage'] = $this->notifyResponse['ErrorMessage'];
    $response['OrderId'] = $this->notifyResponse['OrderId'];
    $response['CustomerId'] = $this->notifyResponse['CustomerId'];
    $response['MailSent'] = $this->notifyResponse['MailSent'];
    $response['Timestamp'] = time();

    return json_encode($this->notifyResponse);
  }