How can I ban a username on my site using php & MySQL?

[Justsomeguy]

I want to able to ban usernames on my site. I've got an interface for site admins to use and i've set up a database already. I don't want to ban IP addresses because there are ways around that. I know that people can just sign up again to avoid the ban, but I want to start with the basics for now, I can always make changes later. Does anyone know a script that can check the username from the session and cross reference it with the usernames from the database and if there's a match, the user will be redirected to another page?

Thanks in advance,
Justsomeguy :)

[JKing]

Do you have a status field or similar field for users? You could set that to "banned" or if that is not an option create another field to be used as a flag for banned users. Then check to see if the user is not flagged before allowing them access.