anti "BACK" button

[eluser]$ilovephp[/eluser]
Hello There.

My situation is i have a login form, works fine, sets the session data. But the problem is, after i login, i can hit the back button of my browser and it will give me the login form again. Sessions isn't destroyed yet. and isn't it annoying to see that the browser will bring you to login form although you have already logged in.

how do you guys solve this problem? Any tips?