id | performer_id | review | rateNum
$countReviews = OrdersHasReviewsRating::find()
->asArray()
->where(['performer_id' => Yii::$app->user->id])
->all();
$sql = 'SELECT SUM(`rateNum`) as `sum` FROM `' . OrdersHasReviewsRating::tableName() . '` WHERE `performer_id`=:performer_id';
$ratingSummary = Yii::$app->db->createCommand($sql)
->bindValue(':performer_id', Yii::$app->user->id)
->queryScalar(); // или ->queryOne();