login.php page is viewed when user hits back button

[oculus]

Hi, I'm having trouble with this. I created login.php and when the user is logged in successfully, he is able to be redirected to the index.php. Visitors can't access index.php unless authenticated and successfully logged in from the login.php. Now the problem is that, when a user hits "back button" or types the URL ...login.php, he can still view the login form. I'm trying not to allow such action. Is it possible to redirect the user to the index.php when he accesses the login.php?

Answers are much appreciated. Thanks