RangeHeader\RangeHeader::getContentRangeHeader PHP Method

    public function getContentRangeHeader()
    {
        return 'bytes ' . $this->getByteRangeSpec() . '/' . $this->filesize;
    }

 public function serve($path)
 {
     $filesize = filesize($path);
     $fp = fopen($path, 'r');
     if (!isset($_SERVER['HTTP_RANGE'])) {
         header('HTTP/1.1 200 OK');
         header('Content-Length: ' . $filesize);
         header('Accept-Ranges: bytes');
         fpassthru($fp);
     } else {
         $range = new RangeHeader($_SERVER['HTTP_RANGE'], $path);
         if (!$range->isValid()) {
             header('HTTP/1.1 416 Requested Range Not Satisfiable');
             header('Content-Range: ' . $range->getContentRangeHeader());
             exit;
         }
         $length = $range->getLength();
         header('HTTP/1.1 206 Partial Content');
         header('Content-Length: ' . $length);
         header('Content-Range: ' . $range->getContentRangeHeader());
         $start = $range->getFirstBytePosition();
         if ($start > 0) {
             fseek($fp, $start, SEEK_SET);
         }
         $chunk_size = 4096;
         while ($length) {
             $read = $length > $chunk_size ? $chunk_size : $length;
             $length -= $read;
             echo fread($fp, $read);
         }
     }
     fclose($fp);
 }