ShoppingCart_Controller::buyableFromRequest PHP Method

    protected function buyableFromRequest()
    {
        $request = $this->getRequest();
        if (SecurityToken::is_enabled() && !self::config()->disable_security_token && !SecurityToken::inst()->checkRequest($request)) {
            return $this->httpError(400, _t("ShoppingCart.InvalidSecurityToken", "Invalid security token, possible CSRF attack."));
        }
        $id = (int) $request->param('ID');
        if (empty($id)) {
            //TODO: store error message
            return null;
        }
        $buyableclass = "Product";
        if ($class = $request->param('Buyable')) {
            $buyableclass = Convert::raw2sql($class);
        }
        if (!ClassInfo::exists($buyableclass)) {
            //TODO: store error message
            return null;
        }
        //ensure only live products are returned, if they are versioned
        $buyable = Object::has_extension($buyableclass, 'Versioned') ? Versioned::get_by_stage($buyableclass, 'Live')->byID($id) : DataObject::get($buyableclass)->byID($id);
        if (!$buyable || !$buyable instanceof Buyable) {
            //TODO: store error message
            return null;
        }
        return $this->cart->getCorrectBuyable($buyable);
    }