portal/app/Http/Resources/PackageResource.php

<?php

namespace App\Http\Resources;

use App\Models\Order;
use App\Models\PackingList;
use Illuminate\Http\Resources\Json\JsonResource;

class PackageResource extends JsonResource
{
    /**
     * Transform the resource into an array.
     *
     * @param  \Illuminate\Http\Request  $request
     * @return array
     */
    public function toArray($request)
    {

        $originalPackingList = $this->packingList->owner instanceof PackingList ? $this->packingList->owner : $this->packingList;

        return [
            'id' => $this->id,
            'type' => $this->type,
            'description' => $this->description,
            'width' => floatval($this->width),
            'height' => floatval($this->height),
            'length' => floatval($this->length),
            'weight' => $this->weight,
            'quantity' => $this->quantity,
            'cbm' => (($this->width / 100) * ($this->height / 100) * ($this->length / 100)) * $this->quantity,
            'status' => $this->status,
            $this->mergeWhen($originalPackingList->owner instanceof Order, [
                'order' => New OrderResource($originalPackingList->owner)
            ]),
            'container' => new ContainerResource($originalPackingList->containers()->first()),
            'transport' => new TransportResource($originalPackingList->transports()->first())
        ];
    }
}