php 提示 未定义数组索引 是什么什么

Question

 $pay=array();
            foreach($search_list as $r){
                $payFirstTotal += $r['money'];
                $pay[date('Y/m/d',$r['time'])]['person'] += 1;
                $pay[date('Y/m/d',$r['time'])]['money']  += round($r['money']);
            }

别人的代码最后的结果是

[2020/09/09] => Array
        (
            [person] => 1
            [money] => 11
        )

怎么我的就报错 未定义数组索引: 2020/09/01

这是什么原因？

Answer 1

https://www.cnblogs.com/weilianguang/p/10974428.html