Validation XSS_CLEAN callback, not working?

[eluser]einstein[/eluser]
Hi.
1.I was just wondering dose the order in a validation rule influence the way that the rulle is applyed?

2. I have a callback function, with this rulles: "required|xss_clean|callback_checkActivationCode";
I also have an echo statement in that function and it returns whatever i enter in the input field, dose that look right, i think it should do a replace for all " ' % etc chars.

Thank you