MySQL表达式与yii2的关系

How can I do an Expression in relation?

public function getInterval()
  {
    return $this->hasMany(Notifies::className(), ['DATE(date_add)' => 'DATE(date_add)']);
  } 

It does not work

public function getInterval()
  {
    return $this->hasMany(Notifies::className(), [new \yii\db\Expression('DATE(date_add)') => new \yii\db\Expression('DATE(date_add)')]);
  } 

It does't work either, illegal type error ;[