category resource.php

<?php
 
namespace App\Http\Resources;
 
use Illuminate\Http\Resources\Json\Resource;
 
class CategoryResource extends Resource
{
    /**
     * Transform the resource into an array.
     *
     * @param  \Illuminate\Http\Request
     * @return array
     */
    public function toArray($request)
    {
        return [
            'id' => $this->id,
            'name' => $this->name
        ];
    }
}
 
 
<?php
 
namespace App\Http\Resources;
 
use App\Category;
use Illuminate\Http\Resources\Json\Resource;
 
class PostResource extends Resource
{
    /**
     * Transform the resource into an array.
     *
     * @param  \Illuminate\Http\Request
     * @return array
     */
    public function toArray($request)
    {
        return [
            "title" => $this->title,
            "body" => $this->body,
            'categories' => CategoryResource::collection($this->categories)
        ];
    }
}