public function toXML(DOMElement $parent) : DOMElement
    {
        $doc = $parent->ownerDocument;

        $e = $doc->createElementNS(Constants::NS_MD, 'md:ContactPerson');
        $parent->appendChild($e);

        $e->setAttribute('contactType', $this->getContactType());

        foreach ($this->getContactPersonAttributes() as $attr => $val) {
            $e->setAttribute($attr, $val);
        }

        Extensions::addList($e, $this->getExtensions());

        if ($this->Company !== null) {
            Utils::addString($e, Constants::NS_MD, 'md:Company', $this->Company);
        }
        if ($this->GivenName !== null) {
            Utils::addString($e, Constants::NS_MD, 'md:GivenName', $this->GivenName);
        }
        if ($this->SurName !== null) {
            Utils::addString($e, Constants::NS_MD, 'md:SurName', $this->SurName);
        }
        if (!empty($this->getEmailAddress())) {
            Utils::addStrings($e, Constants::NS_MD, 'md:EmailAddress', false, $this->getEmailAddress());
        }
        if (!empty($this->getTelephoneNumber())) {
            Utils::addStrings($e, Constants::NS_MD, 'md:TelephoneNumber', false, $this->getTelephoneNumber());
        }

        return $e;
    }