Ajax and PHP Register/Login Validation

Question

Is there any benefits of using Ajax when validate Login/Register with PHP? If so, what are the other things that we can do with it besides displaying error messages?

Answer 1

When using ajax the validation is often done with javascript which makes it a lot faster. After the validation the data is sent with ajax to be stored.
When using client side validation, there should also be server side which will be used when javascript is disabled.