invoiceninja/app/Services/PurchaseOrder/PurchaseOrderInventory.php

<?php
/**
 * Invoice Ninja (https://invoiceninja.com).
 *
 * @link https://github.com/invoiceninja/invoiceninja source repository
 *
 * @copyright Copyright (c) 2023. Invoice Ninja LLC (https://invoiceninja.com)
 *
 * @license https://www.elastic.co/licensing/elastic-license
 */

namespace App\Services\PurchaseOrder;

use App\Models\Product;
use App\Models\PurchaseOrder;

class PurchaseOrderInventory
{
    private PurchaseOrder $purchase_order;

    public function __construct(PurchaseOrder $purchase_order)
    {
        $this->purchase_order = $purchase_order;
    }

    public function run()
    {
        $line_items = $this->purchase_order->line_items;

        foreach ($line_items as $item) {
            $p = Product::query()->where('product_key', $item->product_key)->where('company_id', $this->purchase_order->company_id)->first();

            if (!$p) {
                continue;
            }

            $p->in_stock_quantity += $item->quantity;
            $p->saveQuietly();
        }

        $this->purchase_order->status_id = PurchaseOrder::STATUS_RECEIVED;
        $this->purchase_order->save();

        return $this->purchase_order;
    }
}