Revison 1
The following program was written for my company's time keeping system which utilizes an LDAP database for authentication and a MySQL database for time-keeping, account access control, etc.

If a user has >= 5 unsuccessful logins, it locks the account for 5 minutes. Once a successful LDAP bind has occured, the $_SESSION vars are set and the authorization process is bypassed until the user logs out or the session expires.