Link.FYI

    $content = $filesystem->read($object['path']);
            $xmp_data_start = strpos($content, '<x:xmpmeta');
            $xmp_data_end = strpos($content, '</x:xmpmeta>');
            $xmp_length = $xmp_data_end - $xmp_data_start;
            $xmp_data = substr($content, $xmp_data_start, $xmp_length + 12);

            $document = new DOMDocument();
            $document->loadXml($xmp_data);
            $xpath = new DOMXpath($document);

            /**
             * most likely a bit hackish.. thats how I do get all namespaces...
             */
            $results = preg_match_all('_xmlns:([A-Za-z]+)="(.*)"_U', $xmp_data, $matches);
            foreach($matches[1] as $key => $alias){
//                echo "registering $alias for ".$matches[2][$key]."\n";
                $xpath->registerNamespace($alias, $matches[2][$key]);
            }