下面是最简单的:
            <login>
session_start();
$password = md5($PassWd);
$adminlogin[0] = $UserName;
$adminlogin[1] = $password;
session_name($adminlogin);
session_register("adminlogin");
...................................................
             <logout>
session_start();
session_unregister("adminlogin");
session_destroy();
...................................................
                  调用
session_start();if(!$adminlogin || $adminlogin[0] != $adminuser || $adminlogin[1]!=md5($adminpass)){ 
header("location:login.php");
}