If you want to add BB/Forum type styling functionality to your custom forum, message board, CMS, guestbook or anything else you can use this handy little function which includes my favourite tags (which happen to be XHTML compliant). If the style could not be applied by the standard tag behaviour, I have put an inline style or a class name (if the inline style would be too bloated).

EDIT:
URL to function: http://www.vipluke.myfreeola.com/examples/bbtest.txt
(Code example of BB code was a bad idea on a forum)

Example use:

$bbtext = "[quote]This is a quote[/quote]";
echo bb2html($bbtext);


Hopefully this may help someone.

:)