public function getMessageCount()
    {
        if ($this->getResultCode() === self::RC_SUCCESS_NO_MESSAGES) {
            return 0;
        }

        $node = $this->getFirst('//epp:epp/epp:response/epp:msgQ');
        if ($node === null) {
            return null;
        }

        return (int) $node->getAttribute('count');
    }