XHTML_Validator: Validate XHTML without external PHP extensions

The XhtmlValidator can be used to validate XHTML documents. It uses only the expat extension functions always available under since PHP 3 and it does not need other external XML processing extensions.

The class parses the documents and check whether the tags and attributes used by the documents are allowed within the XHTML standard.

If validation errors are found, highlighted error messages and offending document line numbers will be returned.

This is an experimental class, so you should double check your code with <a href="http://validator.w3.org">the w3c validator</a>, as in only 1000 lines of code the XhtmlValidator lacks support for Encoding and Doctype validation