<?php 
$files = array( 'ga.js' => 'https://js.createsend1.com/javascript/copypastesubscribeformlogic.js' ); 
if(isset($files[$_GET['file']])) { 
if ($files[$_GET['file']] == 'ga.js'){ 
header('Expires: '.gmdate('D, d M Y H:i:s \G\M\T', time() + ((60 * 60) * 48))); 
} else { 
header('Expires: '.gmdate('D, d M Y H:i:s \G\M\T', time() + (60 * 60))); 
} echo file_get_contents($files[$_GET['file']]); 
} ?>