Consolidated Login Page for Multiple Domains

I need a consolidated login page that will use the form POST method to send the username/password entered to a specific login URL, based on the username. The URL used to process the username/password will vary based on the username entered. For example: entering username: user1 and a password will post the data to a specific login page using a POST comment: --form action="[login to view URL]" method="post"-- 2nd example: entering username: user2 and a password will post the data to a different login page at a different URL: --form action="[login to view URL]"-- This system will need an admin panel that allows the admin to specify the username and the URL that the username and password will post to. The consolidated login form exists on a different server than the actual login page. The system for this can be written in PHP.