Gareth Heyes has a recent post pointing out the port of a project of his, CSSReg (a filtering tool for user-provided stylesheets) over to PHP.

Just a quick post to mention the excellent work by Norman Hippert aka @thewildcat, he successfully converted my Javascript based CSSReg into PHP. I was meaning to do this but never found the time so it's pretty awesome that not only did thewildcat convert the code but found some nice bugs in my code and fixed them. Great work Norman thanks very much!

You can see a demo of it here and grab the source as a download here. You can find out more about the origins of CSSReg (and some of its siblings) in this other post from Gareth.