<?php if ($_GET['value'] == 'off') header('X-DNS-Prefetch-Control: off'); else if ($_GET['value'] == 'on') header('X-DNS-Prefetch-Control: on'); else if ($_GET['value'] == 'foo') header('X-DNS-Prefetch-Control: foo'); $fake_domain = "www." . rand() . ".invalid"; ?> <html> <body> <a href='http://<?php echo $fake_domain ?>/'><?php echo $fake_domain ?></a> </body> </html>