Question

Is there a way to detect whether a user is disconnected from internet or not? The way that stackoverflow does when you want to post a question. I couldn’t think of any approach to do that. Could someone shed some light on the subject?

Answer 1

You can send AJAX-request to PHP script when windows is closed:

window.onbeforeunload = function(){
    // Request goes here
}

Alternativly you can use websocket-technology (you can use phpDaemon) to connect with server permanently so you will know when user is disconnected from internet or your site or pereodicly (use setInterval function) ping your server.