PHP创建zip存档

Question

我正在创建一个zip存档，但它不起作用。 Error_log.txt中没有记录错误。我在ajax上请求一个zip存档，而ajax的响应是空的，$_SESSION['uid']代码看起来像这样。

$folder = md5($array->id);
        $this->deleteIfExists($folder);

        $zip = new ZipArchive();
        $name = "users/".$folder."/".$_SESSION['uid'].".zip";

        if($zip->open("users/".$folder."/".$_SESSION['uid'].".zip", ZIPARCHIVE::CREATE) != TRUE){
        echo "Doesn't work :-(";        
        }       

        $zip->addFile("users/".$folder."/client_agree/original_".$array->id.".jpg", "agree.jpg");
        /*
        foreach(json_decode($array->imgs) as $key => $val){
        $zip->addFile("users/".$folder."/client_agree/original_".$val.".jpg", $val.".jpg");     
        }
        */
        $zip->close();

        echo $_SESSION['uid'];