PHP 5 introduced a number of new XML extensions: SOAP, SimpleXML, XSL, DOM

Older XLST and DOMXML were removed in favor of their newer counterparts.

All XML extensions now use a single XML parsing library, LibXML2, unlike the older Expat this library is too big to bundle, however it is available by default on most systems.

Additional XML extensions for PHP 5 are available from PECL repository (XmlReader & XmlWriter)