App\Models\Store\Order::getShipping PHP Method

    public function getShipping()
    {
        if (!$this->address) {
            return 0;
        }
        $rate = $this->address->shippingRate();
        $total = 0;
        $primaryShipping = 0;
        $nextShipping = 0;
        //first find the highest shipping cost, and use that as a base
        foreach ($this->items as $i) {
            if ($i->product->base_shipping > $primaryShipping) {
                $primaryShipping = $i->product->base_shipping;
            }
        }
        //then add up the total
        foreach ($this->items as $i) {
            if ($primaryShipping === $i->product->base_shipping) {
                $total += $i->product->base_shipping * 1 + ($i->quantity - 1) * $i->product->next_shipping;
            } else {
                $total += $i->quantity * $i->product->next_shipping;
            }
        }
        return $total * $rate;
    }