Order::getProductsCost PHP Method

    public function getProductsCost()
    {
        $cost = 0;
        $products = $this->productsChanged ? $this->_orderProducts : $this->products;
        foreach ($products as $op) {
            $cost += $op->price * $op->quantity;
        }
        return $cost;
    }

 public function checkAvailable(Order $order)
 {
     return $order->getProductsCost() >= $this->available_from;
 }