设置数组输入的自定义验证消息(在我的情况下选择)我在 Request 类中使用了 messages()方法:

To set custom validation message for array input (select in my case) I used messages() method in my Request class:

public function messages(){
    $messages = [];
    foreach ($this->request->get('category') as $key => $val) {
        $messages['category.'.$key.'.required'] = 'Выберите подраздел';
    }
    return $messages;
}