automatic session expiration
I am facing a strange scenario. basically on my every web page i am doing

    session_start();
    if(!isset($_SESSION['login']))
    	header("Location: login.php");

to ensure every user has logged in first. I am working in chrome and what happens is if I login to my web application and open any page it works fine. At the same time if, in another tab, I login to my hosting server, I am logged out of my web application. If I login to my application again, I am logged out of my hosting server!!

What am I doing wrong? is there a problem the way I am checking or setting the session variable?
automatic session expiration
===

I am facing a strange scenario. basically on my every web page i am doing

    session_start();
    if(!isset($_SESSION['login']))
    	header("Location: login.php");

to ensure every user has logged in first. I am working in chrome and what happens is if I login to my web application and open any page it works fine. At the same time if, in another tab, I login to my hosting server, I am logged out of my web application. If I login to my application again, I am logged out of my hosting server!!

What am I doing wrong? is there a problem the way I am checking or setting the session variable?