Sonata\Component\Basket\Basket::isValid PHP Method

    public function isValid($elementsOnly = false)
    {
        if ($this->isEmpty()) {
            return false;
        }
        foreach ($this->getBasketElements() as $element) {
            if ($element->isValid() === false) {
                return false;
            }
        }
        if ($elementsOnly) {
            return true;
        }
        if (!$this->getBillingAddress() instanceof AddressInterface) {
            return false;
        }
        if (!$this->getPaymentMethod() instanceof PaymentInterface) {
            return false;
        }
        if (!$this->getDeliveryMethod() instanceof ServiceDeliveryInterface) {
            return false;
        }
        if (!$this->getDeliveryAddress() instanceof AddressInterface) {
            if ($this->getDeliveryMethod()->isAddressRequired()) {
                return false;
            }
        }
        return true;
    }