YII2 Custom validation is not working with custom function model rule

I am trying to implement with custom function in model its not working i am not getting what's wrong in my code. i am trying to call with basic later i will put my condition.

Here is model code

public function rules()
    {
        return [
            ['mobile_number', 'required'],
            ['mobile_number', 'myfunction'],

        ];
    }

public function myfunction($attribute,$params)
    {
             $this->addError($attribute, 'You have already submitted');

    }

Here is controller code

public function actionCreate()
    {
        $model = new Createuser();

        if ($model->load(Yii::$app->request->post()) && $model->save()) {
            return $this->redirect(['view', 'id' => $model->id]);
        } else {
            return $this->render('create', [
                'model' => $model,
            ]);
        }
    }

its not assiging the error to a form-field.

Thanks in advance.

Code is fine. it was error with Dynamic Form validation.