public function __construct(SimpleXMLElement $xml = null)
 {
     parent::__construct($xml);
     if (is_null($xml)) {
         return;
     }
     $this->id = (string) $xml->id;
     $this->title = (string) $xml->title;
     $this->thumbUrl = (string) $xml->thumbUrl;
     $this->description = (string) $xml->description;
     $this->tags = (string) $xml->tags;
     $this->url = (string) $xml->url;
     $this->sourceLink = (string) $xml->sourceLink;
     $this->credit = (string) $xml->credit;
     if (count($xml->licenseType)) {
         $this->licenseType = (int) $xml->licenseType;
     }
     $this->flashPlaybackType = (string) $xml->flashPlaybackType;
     $this->fileExt = (string) $xml->fileExt;
 }