how to fix this error?

[eluser]patrickpopowicz[/eluser]
First, nowhere in the above code do you set the sig_key in the session, so when the callback is being tested, it will return FALSE every time causing the validation to fail. Even then you are not requiring it in your validation rule.

Second, you didn't rework the code at all. You are still using the POST data to set variables before you are validating the data, which you are then using to make calls to the database.

Clean up your code, there are many more issues with the code than just the validation.