1. How can I have a field be unique? As in, only one user can have the same value for the field, like a username.
2. How can I have two fields to be required to run a php callback? Say, a field for username and field for password. Then, after the validation is made, to have only the username field show.
3. How can I have "thank you" "error" when the field has been updated? I tried returning true with $error = 'Thank you for joining blah';