Typically, no, you can't control how the back button works. Though, if the intent is to only allow them onto that page once, you can semi-control it with sessions. On the page you want to control, set a session variable, just stating that they've been there. But before anything on that page, set a check to see if that variable already exists. If it does, redirect with header. This way, the first time they go to that page, the session variable will be set. The second time they go to that page, whether it's through a link, the back button, manually typing in the url, whatever, they'll be redirected. Only workaround I can really think of.
The problem really goes back to the whole "php is server side" logic. The back button is controlled by the browser (client side), and as far as I know, is pretty hard to control even with a client side scripting language.
