Is redirect.php on the same host? If so, consider using require instead. Otherwise you'll need to proxy the request to redirect.php yourself.

Your suggestion won't work.

I tried this and won't work:
1) create redirect.php
<?php
require("redirect_include.php");
?>
2) create redirect_include.php
<?php
header( 'Location: http://www.xyz.com' ) ;
?>

How can I redirect to another page and stay on the same browser?