code: function toXML()
      {
          $xml = new SimpleXMLElement("<?xml version=\"1.0\"?><contacts></contacts>");
          $contactsDom = dom_import_simplexml($xml);
  
          foreach ($this->contacts as $contact) {
              $contactDom = dom_import_simplexml($contact->toXML(false));
              $contactsDom->appendChild($contactsDom->ownerDocument->importNode($contactDom, true));
          }
  
          return new SimpleXMLElement($contactsDom->ownerDocument->saveXML());
      }
docs: Serialization to a simple XML element.
  
  @return \em SimpleXMLElement
  Generate a XML element from the contact object.