protected function buildGetStatusPayload($messageId)
    {
        $xml = new \SimpleXMLElement(
            '<?xml version="1.0" encoding="ISO-8859-1"?>'.
            '<!DOCTYPE STATUSREQUEST SYSTEM "http://127.0.0.1:80/psms/dtd/requeststatusv12.dtd">'.
            '<STATUSREQUEST VER="1.2"></STATUSREQUEST>'
        );

        $user = $xml->addChild('USER');
        $user->addAttribute('USERNAME', $this->username);
        $user->addAttribute('PASSWORD', $this->password);

        $guid = $xml->addChild('GUID');
        $guid->addAttribute('GUID', $messageId);

        return $xml->asXml();
    }