PHP download.php check referer

does anyone know the code to check the referer in a download.php?

I have taken the following code directly from http://php.exocrew.com/?view=scripts (FormMail)

$referer_c = "1";
$referer = array("mysite.com","www.mysite.com");
$fail = "http://somesite.com/fail.html";

if($referer_c=="1") {
if(!isset($_REQUEST['grant'])) { // Check if user hasn't given a value for grant using url

while(list($key,$val)=each($referer)) {
if(strstr($_SERVER['HTTP_REFERER'],$val)) {
$grant = 'true';
} // End giving grant a value
} // End while
} // End if grant

if($grant!='true') {
header("Location: $fail");
exit;
}
}

But it cant be trusted as some browsers doesn't set the REFERER. I would rather prefer setting a cookie at the place where users gets the link to download the file, and then at download.php verify that the cookie exists.