I use php tidy to process html input in my database,
$fragment = tidy_repair_string($dom->saveHTML(), array(\'output-xhtml\'=>1,\'show-body-only\'=>
If you are on a RedHat / CentOS / Fedora linux box and have root access to your server you can run...
yum install php-tidy
as root. Then restart apache and that should get you going.
There may be errors about missing dependencies that need to be added but usually the above command will be all you need.
Other distributions will have slightly different commands but something similar should be available.
On windows you need to install it manually. Instructions can be found here... http://devzone.zend.com/article/761#Heading3