PHP Cookie and "Cannot modify header information"

Today i use setCookie in my project and this code is the most top line

but they warning "Cannot modify header information"

I used ob_start(); but this code did not help anything

so for me i found this solution

Please check your all file encoding because this error happen with UTF8 with signature

(include have some strange line empty)

Change it to UTF8 without signature can help.

cheers.