The HTTP/1.1 ask for an absolute URI with the parameter "location:". Some explorer accept relative paths, but your problem may come from here.
If it's an absolute path on the server, his configuration may be different from your local file. Check if /content is really in the root of the server (and not in a /www or thing like that).
Here a little code you could use to test your global variables.
<?php
/* Redirection to an other webpage in the same file */
$host = $_SERVER['HTTP_HOST'];
$uri = rtrim(dirname($_SERVER['PHP_SELF']), '/\\');
$extra = 'mypage.php';
header("Location: http://$host$uri/$extra");
exit;
?>`