login control

[mshen]

I am buiding a PHP-MySQL application.I need to control the user login.

I like each user account (user name/password) only can login one time at the same time.that mean you can not login in if other people already login using your user name &password.

I need to know how to do this with PHP/MySQL.Please give me a idea /URL if you can.

thanks a lot

[steadyguy]

You could try locking the user/passwd table with SQL:

"LOCK TABLES users WRITE"

If you need to lock more tables, just list them in a comma-sepparated list at the end: "... users WRITE, foo WRITE, bar WRITE, ..."

If the table is locked like this, only the user with the lock can read or write to it. Of course, if it is already locked, then you'll have to wait until it unlocks, so you should setup a timeout to unlock it, if the user isn't active, and when they log out: "UNLOCK TABLES" is the SQL.

Does that help?

[m_tt]

You could just create an "active users" table and verify that the user/session is not in that table.

[m_tt]

I use something similar to what I posted above but I log the username, password, session id, and set a "deactivate" time. The deactivate time will "time-out" the user after x number of minutes of inactivity. If they refresh the page or go to another page the deactivate time is updated.. I use a cron to remove the timed-out sessions.

[mshen]

May I do this only using PHP and MySQL,NOT Corn.

Thanks

[steadyguy]

If you use the SQL method, cron is not necessary

[Weedpacket]

You could have the login script clean expired sessions out of the table as part of its job (before it attempts to log the user in).