PHP实现HTTP断点续传的方法

<?php
/**
 * php-http断点续传实现
 * @param string $path: 文件所在路径
 * @param string $file: 文件名
 * @return void
 */
function download($path,$file) {
  $real = $path.'/'.$file;
  if(!file_exists($real)) {
    return false;
  }
  $size = filesize($real);
  $size2 = $size-1;
  $range = 0;
  if(isset($_server['http_range'])) {
    header('http /1.1 206 partial content');
    $range = str_replace('=','-',$_server['http_range']);
    $range = explode('-',$range);
    $range = trim($range[1]);
    header('content-length:'.$size);
    header('content-range: bytes '.$range.'-'.$size2.'/'.$size);
  } else {
    header('content-length:'.$size);
    header('content-range: bytes 0-'.$size2.'/'.$size);
  }
  header('accenpt-ranges: bytes');
  header('application/octet-stream');
  header("cache-control: public");
  header("pragma: public");
  //解决在ie中下载时中文乱码问题
  $ua = $_server['http_user_agent'];
  if(preg_match('/msie/',$ua)) {
    $ie_filename = str_replace('+','%20',urlencode($file));
    header('content-dispositon:attachment; filename='.$ie_filename);
  } else {
    header('content-dispositon:attachment; filename='.$file);
  }
  $fp = fopen($real,'rb+');
  fseek($fp,$range);
  while(!feof($fp)) {
    set_time_limit(0);
    print(fread($fp,1024));
    flush();
    ob_flush();
  }
  fclose($fp);
}