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);
}