Tim Koschuetzki has created and posted a new tutorial today that talks about working with XML documents with PHP's DOM Library (the PHP5 version) to create, query and update current documents.
The PHP 4 DOMXML extension has undergone some serious transformation since PHP5 and is a lot easier to use. Unlike SimpleXML, DOM can, at times, be cumbersome and unwieldy. However, it is often a better choice than SimpleXML. Please join me and find out why.
He breaks it out into a few different tasks - saving documents, using XPath queries, updating the contents of an XML file, working with namespaces and playing nice with SimpleXML.