static bool http\Env::setResponseHeader(string $header_name, [mixed $header_value = NULL[, int $response_code = 0[, bool $replace = true]]]

Set a response header, either replacing a prior set header, or appending the new header value, depending on $replace.

If no $header_value is specified, or $header_value is NULL, then a previously set header with the same key will be deleted from the list.

If $response_code is not 0, the response status code is updated accordingly.