Good form class?

I'm looking for a good class to manage forms. It doesn't need to do anything with the form itself, I'm looking for something that does form validation on the processing side. I've looked on phpclasses, but everything I found was either insecure (passing data about the form through hidden form fields) or just not what I needed. Any ideas? -- The above message is encrypted with double rot13 encoding. Any unauthorized attempt to decrypt it will be prosecuted to the full extent of the law.