It’s a common problem of CodeIgniter. Some times, browser take cache of the page. it’s fine.But problem is for the application which has login or authentication system.If browser takes cache and also after logout when user click back button then also display the login page from cache.so this time other if other user use the same pc/laptop then he can simply see the content of the page which is restricted. So for this need to disable storing cache.
Write this bellow code in controller or starting of the page. It’s often happened for codeignitter
header("Expires: Sat, 26 Jul 1997 05:00:00 GMT"); // Date in the past
header("Cache-Control: no-store,no-cache, must-revalidate");
The problem should be solved.This line’s of code force browser not to store any cache for this page.