PHP中如何实现不同权限进入不同页面

<?php

$user_perm_level = 1;

session_start();

$_SESSION[&#39;user_perm_level&#39;] = $user_perm_level;

?>

<?php
session_start();

$user_perm_level = $_SESSION[&#39;user_perm_level&#39;];

?>

<?php
session_start();

$user_perm_level = $_SESSION[&#39;user_perm_level&#39;];

switch($user_perm_level){
  case 1:
    header("location: topage1.php");
    break;
  case 2:
    header("location: topage2.php");
    break;
  case 3:
    header("location: topage3.php");
    break;
  default:
    header("location: topage.php");
    break;
}
?>