# Introduction

XML (eXtensible Markup Language) is a data format for structured document interchange on the Web. It is a standard defined by The World Wide Web consortium (W3C). Information about XML and related technologies can be found at » http://www.w3.org/XML/.

This PHP extension implements support for James Clark's expat in PHP. This toolkit lets you parse, but not validate, XML documents. It supports three source character encodings also provided by PHP: `US-ASCII`, `ISO-8859-1` and `UTF-8`. `UTF-16` is not supported.

This extension lets you create XML parsers and then define handlers for different XML events. Each XML parser also has a few parameters you can adjust.