Chyba nastavovania header()

Zdravím, narazil som na problém s nastavovaním headeru.

Error:
Cannot send header after HTTP headers have been sent (output started at C:\xampp\htdocs\storage\libs\Nette\Diagnostics\Debugger.php:630).

Zdrojový kód:

public function fileDownload($id, $httpResponse)
{
    $file = $this->connection->fetch("SELECT * FROM files WHERE id=?", $id);

    dump(BASE_DIR ."/". $file['path'] ."/". $file['name']);

    if (file_exists(BASE_DIR ."/". $file['path'] ."/". $file['name'])) {
        $httpResponse->setHeader('Content-Description', 'File Transfer');
        header('Content-Type: application/octet-stream');
        header('Content-Disposition: attachment; filename='.basename($file['path'] . $file['name']));
        header('Content-Transfer-Encoding: binary');
        header('Expires: 0');
        header('Cache-Control: must-revalidate');
        header('Pragma: public');
        header('Content-Length: ' . filesize($file['path'] . $file['name']));
        ob_clean();
        flush();
        readfile($file['path'] . $file['name']);
        exit;
    }
}

Vopred ďakujem za pomoc.