This is an XML parser based on PHPs built-in xml extension.
It supports two basic modes of operation: "func" and "event".
In "func" mode, it will look for a function named after each element
(xmltag_ELEMENT for start tags and xmltag_ELEMENT_ for end tags),
and in "event" mode it uses a set of generic callbacks.

Since version 1.2.0 there's a new XML_Parser_Simple class that makes
parsing of most XML documents easier, by automatically providing a stack
for the elements. Furthermore its now possible to split the parser from
the handler object, so you do not have to extend XML_Parser anymore in
order to parse a document with it.