S: function to remove & break URLs

Dear list, does anybody of you know these spammers filling up your guestbook with URLs? With strip_tags, I managed to remove the html tags. But what I want is this: 1. Detect such entries (to hide them by default) 2. Destroy URLs As for 2. I am thinking of adding spaces after at least every 12 characters (or even after every dot) - what do you recommend? Just removing "http://" still leaves the domain behind. A good start could be to replace "." by ". " and "/" by " / ". Any code to share? Cheers Ralf.