$filename = '파일이름';

$file = '서버상의 실제 파일 위치';

header("Content-type: file/unknown");
header("Content-Disposition: attachment; filename=$filename");
header("Content-Description: PHP3 Generated Data");
header("Content-Transfer-Encoding: binary ");
header("Pragma: no-cache");
header("Expires: 0");

if(is_file("$file")){
  $fp = fopen("$file","r");
  if (!fpassthru($fp)){
  fclose($fp);
  clearstatcache($fp);
  }
}