ThinkPHP框架下如何用PHP自带的ZipArchive类打包压缩文件？

public function downloadzip(){
    $catid = $this->request->param('catid/d', 0);
    $id = $this->request->param('id/d', 0);
    $category = getCategory($catid);
    if (empty($category)) {
        $this->error('该栏目不存在！');
    }
        $modelid = $category['modelid'];
        $fieldList = $this->Cms_Model->getFieldList($modelid, $id);
    $attatchs=$fieldList['uploadmaterial']['value'];
    $attatchsarray=explode(',',$attatchs);
    $zip=new \ZipArchive();
    $downpath=[];
    $timefils=date("Ymd",time());
    if(!file_exists('uploads/zip/'.$timefils)){
        mkdir ('uploads/zip/'.$timefils,0777,true);
    }
    $zipName ='uploads/zip/'.$timefils.'/download'.$id.'.zip';
    if($zip->open($zipName,\ZipArchive::OVERWRITE | \ZipArchive::CREATE)==TRUE){
        foreach($attatchsarray as $key=>$value){
            $downpath=dirname(ROOT_PATH).get_file_path($value);
            $downpathname=get_file_name($value); //改文件一定得为本地地址不可以为域名地址
                $zip->addFile($downpath, basename($downpathname));  //basename($downpathname)这个是压缩包里面的文件名称

        }
    }
    $zip->close();
    if(!file_exists($zipName)){
        $this->error('文件创建失败');
    }
    header('Content-Type: application/zip');
    header('Content-disposition: attachment; filename='.$zipName);
    header('Content-Length: ' . filesize($zipName));//文件大小
    readfile($zipName);
}