Yii2条件模型

我对yii2开发的表单有问题。我将一个表单字段设置为integer，并将其连接到另一个模型的属性中

我希望可以将其留空，或输入正确的值，但如果留空值，则会出现错误

public function rules() {
  return [
    [['id_user'], 'integer', 'message' => ERROR_INTEGER],
    [['id_user'], 'exist', 'skipOnError' => true, 'targetClass' => User::className(), 'targetAttribute' => ['id_user' => 'id']],
  ];
}

---

尝试使用

'skipOnEmpty'=>true，

public function rules() {
    return [
        [['id_user'], 'integer', 'message' => ERROR_INTEGER],
        [['id_user'], 'exist', 
            'skipOnError' => true, 
            'skipOnEmpty' => true,
            'targetClass' => User::className(), 'targetAttribute' => ['id_user' => 'id']
        ],
   ];
}

---

尝试使用

'skipOnEmpty'=>true，

public function rules() {
    return [
        [['id_user'], 'integer', 'message' => ERROR_INTEGER],
        [['id_user'], 'exist', 
            'skipOnError' => true, 
            'skipOnEmpty' => true,
            'targetClass' => User::className(), 'targetAttribute' => ['id_user' => 'id']
        ],
   ];
}