Just added a new feature to the PHP DOM extension (will be available in PHP 5.2): DOMNode::getNodePath
From time to time I see people trying to compile domxml (from PHP 4) for PHP 5. While it basically works and is technically possible, I highly recommend to not even try to go this route. There is a very high potential for conflicts with the new dom extension or any other libxml2 based extension (like SimpleXML, XMLReader, XSL, etc). If not today, then maybe in later releases.
Ever thought SimpleXML is too simple? Did you know, you can easily extend the SimpleXMLElement class?
Just wasted some time on an annoying behavior of libxml/PHP5.0/xinclude (you can blame different parts for that :) )
PHP 5.1 is just around the corner (at least RC 1) and some new, but not really groundbreaking XML features come with it (see my ApacheCon slides for more information).
Personally for me, the XML support in PHP 5 is quite feature complete and I don't have any pending TODOs for it. But maybe you have some ideas, what could be improved or what could be newly implemented. This is your chance and I'm really interested in hearing from you. Just leave a comment below. Maybe me or someone else will find the time to actually implement it for PHP 5.x :)