PHP断点续传的原理与实现

<span style="font-family:FangSong_GB2312;font-size:14px;"><span style="font-family:FangSong_GB2312;font-size:14px;">/** $file_size  文件大小 */

      functiongetRange($file_size){

     $range =isset($_SERVER['HTTP_RANGE'])?$_SERVER['HTTP_RANGE']:null;

    if(!empty($range)){

         $range =preg_replace('/[\s|,].*/', '', $range);

          $range =explode('-',substr($range,6));

          if(count($range) < 2 ) {

             $range[1] = $file_size;

          }

         $range =array_combine(array('start','end'),$range);

         if(empty($range['start'])) {

            $range['start'] = 0;

         }

         if (!isset($range['end']) || empty($range['end'])) {

            $range['end'] = $file_size;

         }

         return$range;

     }

     return null;

  }

 </span></span>

<span style="font-family:FangSong_GB2312;font-size:14px;"><span style="font-family:FangSong_GB2312;font-size:14px;">$speed = 512;//此参数为下载最大速度

  $pos =strrpos($file_path, "/");

   $file_name =substr($file_path, $pos+1);

  $file_size =filesize($file_path);

  $ranges =getRange($file_size);

  $fh =  fopen($file_path, "rb");

 header('Cache-control: public');

 header('Content-Type: application/octet-stream');

 header('Content-Disposition: attachment; filename='.$file_name);

 if ($ranges !=null) {

    header('HTTP/1.1 206 Partial Content');

    header('Accept-Ranges: bytes');

    header(sprintf('Content-Length: %u',$ranges['end'] - $ranges['start']));

    header(sprintf('Content-Range: bytes %s-%s/%s', $ranges['start'],$ranges['end'], $file_size));

     fseek($fh,sprintf('%u',$ranges['start']));

 }else{

    header("HTTP/1.1 200 OK");

     header(sprintf('Content-Length:%s', $file_size));

 }

 while(!feof($fh))

 {

     echo  fread($fh, round($speed*1024, 0));

     ob_flush();

     sleep(1);

 }

 ($fh != null)&& fclose($fh);

 </span></span>