Headers Sent?

[Anon]

Does anyone know what causes PHP to send it's default headers?

I have a piece of code that I'm writting that needs to set a cookie, but I keep getting the error that the headers have already been sent. I've narrowed down the file where PHP has decided it needs to send it's headers, but I need to know what triggers the sending of the headers.

What happens is I include a few files and everything is fine, but when I include my database abstraction layer (not call it, just include it) PHP sends headers. So I'd like to know what causes PHP to send headers.

[Anon]

You need to make sure that you have no commands like echo before the setcookie command, another common problem is that people leave whitespace before the opening <? tags, That will cause php to send out headers. When phpsends out headers it basicly means that it started sending information to the browser.

[Anon]

Thanks, it was white space. I had a trailing line after my closing ?> tag in the class I was including.