Redirection if not logged in

[eluser]frist44[/eluser]
I have extended Controller with MY_Controller and added the following:

Code:

if(isset($_SERVER['HTTP_REFERER']))$this->session->set_userdata('prev_url', $_SERVER['HTTP_REFERER']);
        else $this->session->set_userdata('prev_url', base_url());

When a user click to a page that requires them to be logged in, I have this at the start of the page:

Code:

if (!is_logged_in()){
            $this->session->set_userdata('prev_url', base_url() . 'purchase/add');
            redirect(base_url() . 'user/login');
            exit;
        }

However, for some reason the session value 'prev_url' is not getting overwritten. If i comment out the redirect code, it does get written. What gives?

Thanks,
Brandon

[eluser]frist44[/eluser]
...

[eluser]frist44[/eluser]
Ignore for now...Thanks.