php下用cookes实现防盗链的效果代码

example:    

页面: dl.php     
--------------------------------------------------------------------------------------     

<?php       

$id = $_GET['id'];       
$act = $_GET['act'];       

switch($act) {       
default :       
case "display" : displayHTML(); break;       
case "down" : down(); break;       
}       

function displayHTML($id) {       
setcookie("visited", "true");       

// print your HTML.       
}       

function down($id) {       
if(! isset($_COOKIE['visited']) ) print "你盗联?";       

$sql = "select path from TABLE where id=". $id;       
//..............................       
}       
?>       

<a href="dl.php?id=1&act=down">Download Now...</a>