Fejl?

Kode 

Warning: session_start() [function.session-start]: Cannot send session cookie - headers already sent by (output started at /usr/home/web/web209856/index.php:12) in /usr/home/web/web209856/include/session.php on line 21

Warning: session_start() [function.session-start]: Cannot send session cache limiter - headers already sent (output started at /usr/home/web/web209856/index.php:12) in /usr/home/web/web209856/include/session.php on line 21

Kode 

19. function startSession(){
20. global $database;
21. session_start();
22. $this->logged_in = $this->checkLogin();
23. if(!$this->logged_in){
24. $this->username = $_SESSION['username'] = GUEST_NAME;
25. $this->userlevel = GUEST_LEVEL;
26. $database->addActiveGuest($_SERVER['REMOTE_ADDR'], $this->time);
27. }
28. else{
29. $database->addActiveUser($this->username, $this->time);
30. }
31. $database->removeInactiveUsers();
32. $database->removeInactiveGuests();
33. if(isset($_SESSION['url'])){
34. $this->referrer = $_SESSION['url'];
35. }else{
36. $this->referrer = "/";
37. }
38. $this->url = $_SESSION['url'] = $_SERVER['PHP_SELF'];
39. }