需要登录两次（PHP Session）

Question

This is my login.php code :

session_start(); 
ob_start ();

$_SESSION['login'] = "login";

header('Location: http://www.domain.com/folder/home.php');

exit();

This is my home.php code :

session_start(); 

ob_start ();


if (!isset($_SESSION['login'])) 
{
    header('Location: http://www.domain.com/folder/login.php');
    exit();
}

The problem is when I login the first time, it goes to home.php and redirect back to login.php. When I login again, it doesn't redirect me to login.php again.

I see the flow using Firefox Developer Toolbar.

I've used var_dump($_SESSION) to see any whether the session is set. It returns array(0).

Is there any problem with this codes? or is it because of any other problems ?

Thanks :D