PHP安全之register_globals的on和off的区别

<form action='' method='get'>
<input type='text' name='username' value='alex' >
<input type='submit' name='sub' value='sub'>
</form>
<?php
echo 'username::',$username;
echo '<br>sub::',$sub;
echo '<br>GET::';
print_r($_GET);

?>

<?php 
 
 // 当用户合法的时候，赋值 
 
 $authorized = true 
  
 if (authenticated_user()) { 
 
 $authorized=true; 
 
 } 
  
 // 由于并没有事先把 $authorized 初始化为 false， 
 
 // 当 register_globals 打开时，可能通过GET auth.php?authorized=1 来定义该变量值 
 
 // 所以任何人都可以绕过身份验证 
 
 if ($authorized) { 
 
 include"/highly/sensitive/data.php"; 
 
 } 
 
 ?>

<?php// Emulate register_globals on 
 
 if (!ini_get('register_globals')) { 
 
 $superglobals= array($_SERVER,$_ENV,$_FILES,$_COOKIE,$_POST,$_GET); 
 
 if (isset($_SESSION)) { 
 
 array_unshift($superglobals,$_SESSION); 
 
 } 
 
 foreach ($superglobals as $superglobal) { 
 
 extract($superglobal,EXTR_SKIP); 
 
 } 
 
 } 
 
 ?>

<?php// Emulate register_globals off 
 
 functionun register_GLOBALS(){ 
 
 if (!ini_get('register_globals')) { 
 
 return; 
 
 } 
 
 // Might want to change this perhaps to a nicer error 
 
 if (isset($_REQUEST['GLOBALS']) || isset($_FILES['GLOBALS'])) { 
 
 die('GLOBALS overwrite attempt detected'); 
 
 } 
 
 // Variables that shouldn't be unset 
 
 $noUnset= array('GLOBALS','_GET','_POST','_COOKIE','_REQUEST','_SERVER','_ENV','_FILES'); 
 
 $input=array_merge($_GET,$_POST,$_COOKIE,$_SERVER,$_ENV,$_FILES,isset($_SESSION) &&is_array($_SESSION) ?$_SESSION: array()); 
 
 foreach ($input as $k=>$v) { 
 
 if (!in_array($k,$noUnset) && isset($GLOBALS[$k])) { 
 
 unset($GLOBALS[$k]);  
 
 } 
 
 } 
 
 } 
  
 unregister_GLOBALS(); 
 
 ?>