Why do I get only one row with fetchAll? [closed]

I have this statement. It should return me more results, but instead returns me only one?

    public function getCartProducts($customerId): bool|CartModel
    {
        $statement = $this->connection->prepare("SELECT ROUND(SUM(product.price * cartitem.quantity)) as totalprice, product.productid, product.imagepath, product.name, product.price, cartitem.quantity FROM cart_item as cartitem LEFT JOIN product as product ON cartitem.product_id = product.productid LEFT JOIN cart AS cart ON cart.cart_id=cartitem.cart_id WHERE customer_id=:customerId AND is_ordered = 0;");
        $statement->execute(['customerId' => $customerId]);
        $rows = $statement->fetchAll();