frontend\modules\tweet\models\Tweet::afterSave PHP Method

    public function afterSave($insert, $changedAttributes)
    {
        parent::afterSave($insert, $changedAttributes);
        (new UserMeta())->saveNewMeta($this->type, $this->id, 'follow');
        (new NotificationService())->newPostNotify(\Yii::$app->user->identity, $this, $this->atUsers);
    }