Odoslanie formulara a curl request

Ahojte,
nemal niekto takyto problem:
Odoslem formular a pri vykonavani funkcie na $form->onSuccess[] chcem odoslat CURL request.
Vyhodi mi to chybu:
User Notice
Possible problem: you are sending a HTTP header while already having some data in output buffer. Try OutputDebugger or start session earlier.