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

[cole at colejoplin.com]

PHP and JS hoops are not a very simple or effective way to go. Don't  
work so hard! I have used sessions quite a bit. They are simple, with  
some obscure gotchas, but aren't a big deal to overcome. I recommend  
reading this:

http://www.sitepoint.com/blogs/2004/03/03/notes-on-php-session-security/

Basically, where this much security required, it's best handled with  
SSL. Aside from that, you really don't need to do anything crazy or  
fancy. IMO, the simple solution is the best.

As for timing, if you're on a shared server, before you start your  
session, you can call ini_set() to control the session timeout.

-- Cole