[UPHPU] Best way to prevent multiple logins from the same account.

[Brady Mitchell]

> Hello all, I have been hacking some code around to see if it is possible to
> prevent multiple logins from the same account. That is, if username/password
> is currently logged in, and someone opens another web browser and tries to
> login with that same username/password it will then redirect them out,
> saying that someone from your account is already currently logged in.

I did this for a project that I was working on a while ago, using 
sessions and storing session info in a db table.

When someone tries to login:

if(username and password combination are valid)
{
     if(user id is in the session table)
     {
         login denied because the user is already logged in
     }
     else
     {
         login and direct to requested page
     }
}

Obviously this is a very brief overview of how it could be done. I'm not 
even sure this is the best way for it to be done. I ended up abandoning 
the previously mentioned project so I haven't dealt with this in a 
production environment.

I suggest reading up on sessions on php.net 
http://us2.php.net/manual/en/ref.session.php.

Also, I like to use the ADODB class (http://adodb.sf.net) for db 
connections, and it makes storing session info in a DB extremely easy. 
So check it out if you're struggling or just want some sample code on 
how to do this.

Brady