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

    public function updateItem($item_form, $add_new = false)
    {
        $quantity = intval(array_get($item_form, 'quantity'));
        $product = Product::find(array_get($item_form, 'product_id'));
        $extraInfo = array_get($item_form, 'extra_info');
        $result = [true, ''];
        if ($product) {
            if ($quantity <= 0) {
                $item = $this->items()->where('product_id', $product->product_id)->get()->first();
                if ($item) {
                    $item->delete();
                }
                if ($this->items()->count() === 0) {
                    $this->delete();
                }
            } else {
                $item = $this->items()->where('product_id', $product->product_id)->get()->first();
                if ($item) {
                    if ($add_new) {
                        $item->quantity += $quantity;
                    } else {
                        $item->quantity = $quantity;
                    }
                } else {
                    $item = new OrderItem();
                    $item->quantity = $quantity;
                    $item->extra_info = $extraInfo;
                    $item->product()->associate($product);
                    if ($product->cost === null) {
                        $item->cost = intval($item_form['cost']);
                    }
                }
                if (!$product->inStock($item->quantity)) {
                    $result = [false, 'not enough stock'];
                } elseif (!$product->enabled) {
                    $result = [false, 'invalid item'];
                } elseif ($item->quantity > $product->max_quantity) {
                    $result = [false, "you can only order {$product->max_quantity} of this item per order. visit your <a href='/store/cart'>shopping cart</a> to confirm your current order"];
                } else {
                    $this->save();
                    $this->items()->save($item);
                }
            }
        } else {
            $result = [false, 'no product'];
        }
        return $result;
    }