- Common PHP Header Functions: header()
- http://php.net/manual/function.header
- setcookie()
- This lets you send cookies to the client without knowing the format for the Set-Cookie header.
- apache_request_headers()
- This provides all of the headers that the client sent, as an associative array.
- headers_sent()
- This returns true or false, depending on whether or not headers have already been sent to the client.
