private function encrypt($string = "")
    {

        $key = $this->config->get('gateway.asanpardakht.key');
        $iv = $this->config->get('gateway.asanpardakht.iv');

        try {

            $soap = new SoapClient("https://services.asanpardakht.net/paygate/internalutils.asmx?WSDL");
            $params = array(
                'aesKey' => $key,
                'aesVector' => $iv,
                'toBeEncrypted' => $string
            );

            $response = $soap->EncryptInAES($params);
            return $response->EncryptInAESResult;

        } catch (\SoapFault $e) {
            return "";
        }
    }