A section of the security chain of PHP code

<?php $ADMIN [Defaulturl] = "http://www.163.com/404.htm";//Hotlinking return address
$okaysites = Array ("http://www.163.com/", "http://163.com"); White List
$ADMIN [Url_1] = "http://www.163.com/download/";//Download Location 1
$ADMIN [url_2] = "";//download location 2, and so on

$reffer = $HTTP _referer;
if ($reffer) {
$yes = 0;
while (the list ($domain, $subarray) = each ($okaysites)) {
if (Ereg ($subarray, "$reffer")) {
$yes = 1;
}
}
$theu = "url". " _"." $site ";
if ($ADMIN [$theu] and $yes = 1) {
Header ("Location: $ADMIN [$theu]/$file");
} else {
Header ("Location: $ADMIN [Defaulturl]");
}
} else {
Header ("Location: $ADMIN [Defaulturl]");
}

?>

How to: Save the above code as dao4.php,
For example, test Validatecode.rar in the site Http://163.com/download,
The download connection is represented by the following code.

File name? site=1&file= files

For example, the following URL. Copy to your site and try it.

Http://www.163.com/dao4.php?site=1&file=validatecode.rar

The above code test is available