Input Filtering

I realize that I need to do some filtering on user input (variables from POSTs or GETs) to prevent errors and security breaches. Has any one written a function to do this. As it is I realize I need to addslashes on anything going into a DB and worry about semi-colons to prevent SQL injection attacks. Is there anything else I need to worry about. I'm using a php 4.2.1 front end to a mysql backend. TIA ---------------- Thanks Jefferson Cowart Jeff@cowart.net Support Open Instant Messaging Protocols http://www.petitiononline.com/openIM/petition.html