WebReference.com has an excerpt posted from one of Packt Publishing's latest PHP-related offerings, "PHP Oracle Web Development: Data processing, Security, Caching, XML, Web Services, and Ajax" (by Yuli Vasiliev). This specific chapter talks about XML-enabled applications and how PHP fits into the mix.

Both PHP and Oracle provide comprehensive support for XML and XML-related technologies. Practically, this means you can perform any XML processing either with PHP or inside an Oracle database. [...] This chapter explains how to effectively use XML techniques and technologies available in PHP and Oracle when building XML-enabled PHP/Oracle applications.

They cover the processing of XML in PHP/Oracle apps (including the SAX, DOM and SimpleXML methods), working with XPath and processing the XML in the other half of the two - Oracle's XML processing functionality.

Check out the Packt website for more information on the book.