关于URL传递函数的问题？快来帮帮我呀，很急！很急！一定给分！！！！

Question

<?php
if (!$_GET['id']) header("Location:sorry.php"); 
?>

Answer 1

<?php
if ($_REQUEST['id']=="") header("Location:sorry.php"); 
?>

Answer 2

<?php
if (@$_GET['id']=="") header("Location:sorry.php"); 
?>
试一下.

Answer 3

<?php
if ($_REQUEST['id']=="") header("Location:sorry.php"); 
?>

Answer 4

$id = $_GET['id'];
if (empty($id)) { header("Location:sorry.php"); }

Answer 5

empty用来测试变数是否已经设定。若变数已存在、非空字串或者非零，则传回 false 值；反之传回 true