Php error. With Nstresser code

Ive linked my DB and built the database, I can create a user but when I log in. I get this? Any ideas how to fix it.

Warning: Cannot modify header information - headers already sent by (output started at /customers/2/2/9/peachsparadise.com/httpd.www/hub/index.php:6) in /customers/2/2/9/peachsparadise.com/httpd.www/hub/@/header.php on line 11

Now the only thing on line 11 is Header(location: hub/login.php);

Pms welcome. I wanna get this working