thinkphp下载MP4视频

    /**     * @param $file  视频路径     * @param $showname 显示下载的视频名称     * @return int|string     */     public function download_file($file,$showname){        if(is_file($file)){            $length = filesize($file);            header("Content-Description: File Transfer");            header('Content-type: video/mp4');            header('Content-Length:' . $length);            if (preg_match('/MSIE/', $_SERVER['HTTP_USER_AGENT'])) { //for IE                header('Content-Disposition: attachment; filename="' . rawurlencode($showname.'.mp4') . '"');            } else {                header('Content-Disposition: attachment; filename="' . $showname.'.mp4' . '"');            }            return readfile($file);        } else {            return('文件已被删除！');        }    }