Use Windows Login in PHP Applications: "As a developer you may run into a situation such as what I had, numerous applications deployed and or created and deployed.
With multiple logins for all the apps, we had to find way to integrate all logins for better management and maintenance.
Since we were using Apache with a PHP server, the solution was to find a way to consolidate the logins usin PHP.
The answer is ldap() (Lightweight Directory Access Protocol), this built in function through PHP, allows you to create username and password schemes using existing Windows authentication."