This article is helpful only if you have the following situation:
A web app which uses facebook login to login its users and if a user is logged out from his/her facebook account through another browser tab, then your app dont know that he is logged out out or not from his facebook account and he/she will remain as logged in your web application.Its ok if you have no problem with this situation.But if you want to forcefully logout the user from your application if he is logged out from his facebook account means you can try this example.This example uses periodic ajax calls to facebook's graph api to check whether the user is logged in or not.
After you have setup your Yii2 advanced application, you now have setup your user authentication for both frontend and backend. However, if you have first logged into frontend, and try to access backend from the same client machine, you see no login screen, but find yourself automatically logged in.
I am writing this guide because I struggled to find a resource that included ALL of the necessary steps to completely separate the frontend from the backend. After reading guides like Configuring different sessions for backend and frontend in yii-advanced-app and yii2 configuring different sessions for backend and frontend in yii advanced application template, there are still steps missing. It is funny how the 2nd one says it is an extension of the first one's article. So I guess, my wiki guide here is yet a 3rd and more complete extension of both of them. I also found a few StackOverflow questions and blog posts regarding this topic. None of them fully worked, and must be missing some magic sauce!