strip_tags() but not only vulnerability
Some time ago I wrote document describing common problem with cleaning up
HTML. PHP manual states some little warning about topic but no solution on
http://www.php.net/strip_tags
Many websites are still vulnerable and similar problems happen not depending
on programming language too often:
http://www.jes.ee/~tonu/strip.php
Please do not start flamewar, I know some people might find this information
useful. Yes, it is not "advanced" and this is why people often do not notice
the problem.
Tõnu