分享一个超好用的php header下载函数(2)

header('Pragma: cache');
    header('Cache-Control: public, must-revalidate, max-age=0');
    header('Accept-Ranges: bytes');
    header('Content-type: ' . $contentType);
    header('Content-Length: ' . $contentLength);

    if ($forceDownload)
    {
        header('Content-Disposition: attachment; filename="' . rawurlencode($fancyName). '"');//汉字自动转为URL编码
  header('Content-Disposition: attachment; filename="' . $fancyName. '"');
    }

header("Content-Transfer-Encoding: binary");

    $bufferSize = 2048;

if ($speedLimit != 0)
    {
        $packetTime = floor($bufferSize * 1000000 / $speedLimit);
    }

$bytesSent = 0;
    $fp = fopen($fileName, "rb");
    fseek($fp, $startPos);

//fpassthru($fp);

    while ($bytesSent < $contentLength && !feof($fp) && connection_status() == 0 )
    {
        if ($speedLimit != 0)
        {
            list($usec, $sec) = explode(" ", microtime());
            $outputTimeStart = ((float)$usec + (float)$sec);
        }

$readBufferSize = $contentLength - $bytesSent < $bufferSize ? $contentLength - $bytesSent : $bufferSize;
        $buffer = fread($fp, $readBufferSize);       

echo $buffer;

ob_flush();
        flush();

$bytesSent += $readBufferSize;

        if ($speedLimit != 0)
        {
            list($usec, $sec) = explode(" ", microtime());
            $outputTimeEnd = ((float)$usec + (float)$sec);

            $useTime = ((float) $outputTimeEnd - (float) $outputTimeStart) * 1000000;
            $sleepTime = round($packetTime - $useTime);
            if ($sleepTime > 0)
            {
                usleep($sleepTime);
            }
        }
    }
   

return true;
}
 ?>