src/ImageResponse.php
private function usesXSendFile()
    {
        return isset($this->headers['x-sendfile']) &&
            isset($this->headers['content-lenght']) &&
            isset($this->headers['content-disposition']);
    }
private function usesXSendFile()
    {
        return isset($this->headers['x-sendfile']) &&
            isset($this->headers['content-lenght']) &&
            isset($this->headers['content-disposition']);
    }
usesXSendFile

@return bool