PHP force download of remote file without reading into memory
if($url = getRemoteFileURL($file_id))
{
  header('Content-Type: application/octet-stream');
  header('Content-Disposition: attachment; filename="abc.zip"');
  header('Content-Transfer-Encoding: binary');
  header('Expires: 0');
  header('Cache-Control: must-revalidate, post-check=0, pre-check=0');
  header('Pragma: public');
  header('Pragma: no-cache');

  readfile($url);  // is there a better function ?
}