PHP session destroy function does not work in Opera

[klax]

I made a login system in PHP and every thing working fine in Google Chrome and Mozilla. But in Opera when I click sign out then it works fine and after that if I press back button in browser then it comes to the previous page (profile page ) and shows the contents in that page even if I logout but if I refresh the page then sessions are destroy properly. I used the following code for session destroy\[code\]session_start();$_SESSION = array();session_destroy();session_unset();\[/code\]I am in a critical stage please help me with a right advise.Thanks in advance