On PHPBuilder.com there's a new tutorial from Octavia Anghel about using the DOM extension to parse XML in a PHP5 application. The DOM functionality makes it simpler than even the older PHP4 DOM functionality to work with XML messaging and documents.

DOM (Document Object Model) is a W3C standard based on a set of interfaces, which can be used to represent an XML or HTML document as a tree of objects. A DOM tree defines the logical structure of documents and the way a document is accessed and manipulated. Using DOM, developers create and build XML or HTML documents, navigate their structures, and add, modify, or delete elements and content. The DOM can be used with any programming language, but in this article we will use the DOM extension for PHP 5. This extension is part of the PHP core and doesn't need any installation.

They include both a sample XML file to parse and the code you'll need to pull it in and make a basic DOM object out of it. Also included is some code showing how to pull out certain pieces of information, recurse through a set of XML values, add new nodes to the structure, remove a node and more.