PHP MySQL step 6 Check New UserName

You can add a server behavior to a user registration page that verifies that the Email is unique before adding that user to your database of registered users. When the user clicks the Submit button on the registration page, the server behavior compares the Email entered by the user against the data stored in a database table of registered users. If no matching Email is found in the database table, the server behavior carries out the insert record operation normally. If a matching Email is found, the server behavior cancels the insert record operation and opens a new page (usually a page alerting the user that the Email is
already taken).