HTML Purifier

HTML Purifier is a standards-compliant HTML filter library written in PHP. HTML Purifier will not only remove all malicious code (better known as XSS) with a thoroughly audited, secure yet permissive whitelist, it will also make sure your documents are standards compliant, something only achievable with a comprehensive knowledge of W3C’s specifications. Tired of using BBCode due to the current landscape of deficient or insecure HTML filters? Have a WYSIWYG editor but never been able to use it? Looking for high-quality, standards-compliant, open-source components for that application you’re building? HTML Purifier is for you!

Official Website: http://htmlpurifier.org/
Codeigniter Plugin Website: http://www.mindloop.be/htmlpurifier-and-the-codeigniter-framework/

Updated:
Working example: http://codeigniter.com/wiki/htmlpurifier/