PHP related skills for file transfer

$fname = 'http://XXXX/MMLDZG.mp3';
$fp = fopen($fname,'rb');
$fsize = filesize($fname);
if (isset($_SERVER[&#39;HTTP_RANGE&#39;]) && ($_SERVER[&#39;HTTP_RANGE&#39;] != "") && preg_match("/^bytes=([0-9]+)-$/i", $_SERVER[&#39;HTTP_RANGE&#39;], $match) && ($match[1] < $fsize)) {   $start = $match[1]; } else {   $start = 0; } @header("Cache-control: public"); @header("Pragma: public"); if ($star--> 0) {
  fseek($fp, $start);
  Header("HTTP/1.1 206 Partial Content");
  Header("Content-Length: " . ($fsize - $start));
  Header("Content-Ranges: bytes" . $start . "-" . ($fsize - 1) . "/" . $fsize);
} else {
  header("Content-Length: $fsize");
  Header("Accept-Ranges: bytes");
}
@header("Content-Type: application/octet-stream");
@header("Content-Disposition: attachment;filename=mmdld.mp3");
fpassthru($fp);
fpassthru();//函数输出文件指针处的所有剩余数据。