HTML Class: HTML tag wrapper similar to Perl HTML::Element

This class is an HTML tag wrapper that provides functions to output many types of HTML tags with arguments that control the details of how such tags are generated.

This class is similare to HTML::Element Perl module, and the light counterpart of the advanced PhpWiki modules, which outputs trees of xml objects, not strings as htmlclass.

Features:

- Ensures proper nesting of HTML tags (especially with emacs),
- XHTML (XML) compliant. If the constant XHTML is defined, XHTML conforming tags are returned, otherwise the generated tags are compliant with HTML 4.
- Variable number of content arguments for all tags, not only containers.
- Can NOT do tag nesting checking. (is_contained_in(), may_contain(), is_valid_attribute())