How to know when user closes browser? Chat application

Question

I have a simple chat client set up that allows users to login with a username and stores the messages they write in an sql database. Every 3 seconds, the database simply pri

Answer 1

put online users in a table that will have a field named like 'lastSeen' update this field every few seconds with ajax call..

ajax call be made someting like this :

window.setInterval(function() {
    $.ajax({      
      url: _URL_ENGINE + "/updateLastSeen/?userid=" + userID,
      success: function(data) {

      }
    }); 
}, 2000); // 2000 means 2 seconds

now to query the list of online players u can query them like

select * from players WHERE lastSeen > DATE_SUB(NOW(), interval 40 SECOND) 

hope this helps