it gives me the same error for every variable thath I try to retrive with $_POST
FYI:
You don't retrieve variables with $_POST. Correct is:
With a POST-Request, you retrieve the Array $_POST,which have several indexes.
You are shure, that you have a POST formular (in HTML). And the form elements have the correct name attributes?
BTW: You are getting this error before or after transmitting the form?