代码如下图：这样子在foreach中是无法修改class_history的。正确的应该是去掉??[]判断。

    public function actionY(){$array = ['name'=>'aaa','class_history'=>[['class_name'=>'一班','class_num'=>1],['class_name'=>'二班','class_num'=>2]]];foreach ($array['class_history']??[] as &$item) {$item['class_name'] = '三班';$item['class_num'] = 3;}var_dump($array);}