[howtogeek]

There’s no simple way to do this… and there’s a ton of possible security holes if you do it wrong.

You will need to have a database table to store session information, and check that on every page load.

The iframe approach would need to only indicate that the user was logged on, but make sure you don’t set the password cookie that way… just the sessionid or userid, and then each application would have to check the shared session store.