- print_r: documentation ( source)
<?php
$xml = <<<EOD
<?xml version="1.0" encoding="UTF-8"?>
<gvq:GVQ_Metadata id="dataset_MD" xmlns:updated19115="http://www.geoviqua.org/19115_updates" xmlns:gmx="http://www.isotc211.org/2005/gmx" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:gmd="http://www.isotc211.org/2005/gmd" xmlns:gco="http://www.isotc211.org/2005/gco" xmlns:gvq="http://www.geoviqua.org/QualityInformationModel/4.0" xmlns:gml="http://www.opengis.net/gml/3.2" xmlns:gmd19157="http://www.geoviqua.org/gmd19157" xmlns:un="http://www.uncertml.org/2.0" xmlns:qml="http://qualityml.geoviqua.org/1.0" xsi:schemaLocation="http://www.geoviqua.org/QualityInformationModel/4.0 http://schemas.geoviqua.org/GVQ/4.0/GeoViQua_PQM_UQM.xsd http://www.uncertml.org/2.0 http://qualityml.geoviqua.org/schemas/uncertml/2.0/uncertml.xsd http://qualityml.geoviqua.org/1.0 http://qualityml.geoviqua.org/schemas/qualityml/1.0/qualityml.xsd">
<gmd:fileIdentifier>
<gco:CharacterString>mtri2an1ib</gco:CharacterString>
</gmd:fileIdentifier>
</gvq:GVQ_Metadata>
EOD;
$dom = new DOMDocument;
$dom->loadXML($xml);
$sxe = new SimpleXMLElement($xml);
$namespaces = $sxe->getDocNamespaces(TRUE);
print_r($dom->getElementsByTagNameNS($ns["gmd"], "fileIdentifier"));
?>