Defining header response not working in hiawatha and php

Question

I have a local server and a remote server. On the local server what I'm trying to do works, but the remote server which is hiawatha doesn't.

I'm trying to set a not found header and then respond with the login page. I'm using the following code to do that

if($e === "ErrorSessionExpired")
        {

            header("HTTP/1.0 404 Not Found");
            $output = $this->smarty->fetch("login.tpl");
            echo $output;
            exit();
        }

As I said this works fine on the developing machine, which uses the embedded server of PhpED