If you click the browser back button from any screen, currently it closes everything. It should not close the entire page, but instead go to the previous tab/screen. This only happens in phpmyadmin if you click back immediately after you opened it (without clicking on any other tab or section). That's the normal behaviour users would expect when clicking the back button.
Check out phpmyadmin and you will see that it remembers even the tabs you went through within the history and when you click back it goes to the previous tab or section you have opened.