thinkphp foreach遍历数组并添加属性（下标）

thinkphp如何使用foreach遍历数组并添加属性（下标）
使用下面代码即可

foreach ($list as &$value){
                $from_time=Db::table('txsh_group_chat')->where(['user_id'=>$user_id,'group_id'=>$value['group_id']])->field('latest_time')->find();
                if($from_time['latest_time']==null){
                    $from_time['latest_time']==null;
                }
                $value['count']=$text->get_group_count($value['group_id'],$from_time['latest_time'],$value['latest_time']);
}