note 94935 added to session.examples

This gives me warnings: Warning: session_start() [function.session-start]: Cannot send session cookie - headers already sent by (output started at D:\xampp\htdocs\xslt\session.php:21) in D:\xampp\htdocs\xslt\session.php on line 34 Warning: session_start() [function.session-start]: Cannot send session cache limiter - headers already sent (output started at D:\xampp\htdocs\xslt\session.php:21) in D:\xampp\htdocs\xslt\session.php on line 34 Warning: session_start() [function.session-start]: Cannot send session cookie - headers already sent by (output started at D:\xampp\htdocs\xslt\session.php:21) in D:\xampp\htdocs\xslt\session.php on line 40 Warning: session_start() [function.session-start]: Cannot send session cache limiter - headers already sent (output started at D:\xampp\htdocs\xslt\session.php:21) in D:\xampp\htdocs\xslt\session.php on line 40 Can someone explain why this warnings appear? ---- Server IP: 69.147.83.197 Probable Submitter: 213.91.151.194 ---- Manual Page -- http://www.php.net/manual/en/session.examples.php Edit -- https://master.php.net/note/edit/94935 Del: integrated -- https://master.php.net/note/delete/94935/integrated Del: useless -- https://master.php.net/note/delete/94935/useless Del: bad code -- https://master.php.net/note/delete/94935/bad+code Del: spam -- https://master.php.net/note/delete/94935/spam Del: non-english -- https://master.php.net/note/delete/94935/non-english Del: in docs -- https://master.php.net/note/delete/94935/in+docs Del: other reasons-- https://master.php.net/note/delete/94935 Reject -- https://master.php.net/note/reject/94935 Search -- https://master.php.net/manage/user-notes.php