A quick tip on xpath queries and default namespaces. It looks like the XML-system behind SimpleXML has the same workings as I believe the XML-system .NET uses: when one needs to address something in the default namespace, one will have to declare the namespace using registerXPathNamespace and then use its prefix to address the otherwise in the default namespace living element.
<?php
$string = <<<XML
<?xml version='1.0'?>
<document xmlns="http://www.w3.org/2005/Atom">
<title>Forty What?</title>
<from>Joe</from>
<to>Jane</to>
<body>
I know that's the answer -- but what's the question?
</body>
</document>
XML;
$xml = simplexml_load_string($string);
$xml->registerXPathNamespace("def", "http://www.w3.org/2005/Atom");
$nodes = $xml->xpath("//def:document/def:title");
?>