Warning: Cannot add header information

[albert]

I get this warning:

Warning: Cannot add header information - headers already sent by (output started at /home/sites/site13/web/sunshop/global.php:2179) in /home/sites/site13/web/sunshop/global.php on line 2121

What might be the problem?

Thank you.

[TurnkeyAdmin]

Please do not post same questions in multiple forums.