How to add field to gridview and yii2 model?

Question

Yii

There is a Users model in it there are fields day, month, year
Created by CRUD these fields are displayed separately in the gridview. How to create a new field birthday, for example, which will not be in the database, but it must be composed of day, month, year and displayed in the grid

Answer 1

make a getter method in the model that will form the date of birth, for example:

public function getBirthDay(){
    return $this->day . '.' . $this->month . '.' . $this->year;
}

and work with it like a normal attribute