php json_decode 返回 null 乱码问题

		//用其他语言进行 urldecode ->  jsondecode 后如下（php这样不行）：
		{
			"uid": "jh4Er1fQIioZzONM8cLVJg",
			"nick": "五行缺钱",
			"goods": "",
			"user_source": 3,
			"winning_time": 1577863823,
			"award_status": 1
		},
		{
			"uid": "zumEu93Z8CqYTXRGjHo",
			"nick": "���հ���",
			"goods": "",
			"user_source": 3,
			"winning_time": 1577863823,
			"award_status": 1
		}
		

    //正则替换乱码昵称。匹配模式："nick":"xxx",（需要自己确定）
    public function replaceBadcodeNickInResInfo($res_info, $replace="")
    {
        $tmp1 = urldecode($res_info);
        $r = preg_match_all('|\"nick\"\:\"(.+)\",|iU', $tmp1, $matches);    //i表示区分大小写，U表示非贪婪模式，("nick":"xxx",)这种模式
        if(!empty($r) && !empty($matches[0]) && !empty($matches[1])){
            //逐个对昵称进行编解码尝试，把解码失败的乱码的昵称去掉
            foreach($matches[1] as $key => $value){
                $madeJsonString = '{"a":"'.$value.'"}';
                $dr = json_decode($madeJsonString, true);
                if(empty($dr)){
                    //echo "find bad nick: ".$value."\n";
                    //替换原字符串里的这个乱码的
                    $tmp1 = str_replace($matches[0][$key], '"nick":"'.$replace.'",', $tmp1);
                }
            }
        }
        return json_decode($tmp1, true);
    }