How to Prevent Concurrent User Logins in PHP/MySQL Site?

Question

I am developing the user management portion of a website that will host a webcast. The goal is to prrevent the same user nam (email address) from being used concurrently.

Answer 1

If it is OK to logout an already logged in user if someone else logs in with the same credentials then you could do the following: when a user logs in generate a random ID in your database for that user and the same in a cookie session. The two must match to authenticate.