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！');
        }
    }