easy javascript to detect mobile device with a php variable included

[admin]

 <script>
if( /Android|webOS|iPhone|iPad|iPod|BlackBerry/i.test(navigator.userAgent) ) {
window.location = "http://www.manager.net/registration_iphone.php?class_id="+<?php echo $_GET['class_id']; ?>;
}
</script>

where as in php you use a . to join things in javascripting you use a + sign

?class_id="+<?php echo $_GET['class_id']; ?>