PHP includes optional XML extensions that support Expat parser. XML-related functions in PHP allow you to create a parser to handle valid XML documents. If you are using Apache version 1.3.7, you do not need to add any function libraries. All you need to do is configure PHP using --with-xml.
There are several good examples of creating PHP-based XML parsers in the PHP manual. Additionally, New Riders' Web Application Development with PHP 4.0 has a good overview of using XML in PHP, and one of the authors of the book has written a lot of guides on it.
Just like Java and COM support, PHP's support for XML is still in the early childhood stage of rapid development. If you already have experience in Expat or LibXML, you can use your expertise to skip some content.
Julie Meloni is the technical director of i2i Interactive and a powerful enabler of the Linux and open source community. She has written many books on PHP and other technologies and has become an expert in CNET's long-term contribution.