non va.

ho trovato anche quest'altro

<?php

$referer = $_SERVER['HTTP_REFERER'];
$validDOMAIN = 'tuodominio.ext';

if(!$referer)
{
echo "errore";
exit;
}

$host = explode('.',parse_url($referer)['host']);
$domain = '';
if(count($host)<2)
{
echo "errore";
exit;
}
elseif(count($host)==2)
{
$domain = implode('.',$host);
}else
$domain = implode('.',array_slice($host,1,2));

if($domain!=$validDOMAIN)
{
echo "errore";
exit;
}
?>


<html......></html>