Automatic logout from WordPress after leaving protected area

I have a wordpress site and I need the function so if yo开发者_运维技巧ur logged into a protected page and you leave that page you cannot hit the back button and go back without signing in again.

How to achieve that?

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Well the admin area is always at /wp-admin and id imagine it uses session authentication so why don't you just put a piece of code into your index file, or any other file that gets called on each page load that deletes the session if the url doesn't begin with /wp-admin For example:

if(substr($_SERVER['REQUEST_URI'], 0, 9)!='/wp-admin') {
    session_destroy();
}