I am looking for a way to find out how many tabs are open in my browser. Basically my goal is to handle "keep me in the system." But the problem is that I did not check this checkbox and opened several tabs, and then if I close one tab, it deletes my session. I want to know if the user has checked the Remember Me box, and then he closes the last tab of my website, then I must destroy his session.
You must use cookies to check if you are logged in. You do not need to know what other users see or how many other sites he sees
I assume (and hope) that you cannot, because it means that you will have access to the private data of users - for example. what URL he opened in another tab.
What you do here is a nightmare for me ...