CategoryController.php

<?php

namespace App\Http\Controllers;

use Illuminate\Http\Request;
use App\Models\Category;

class CategoryController extends Controller
{
    public function index()
    {
        return Category::where("parent_id", null)->get();
    }
    
    public function show($id)
    {
        $category = Category::with("parent")->find($id);

        $parents = [];
        $current = $category->parent;
        while($current!=null){
            $parent = Category::find($current->id);
            array_unshift($parents, $parent);
            $current = $current->parent;
        }
        
        $category["parent"] = $parents;
        return $category;
    }
}