exchange/app/Http/Controllers/Api/TarifController.php

<?php

namespace App\Http\Controllers\Api;

use App\Models\Tarif;
use App\Transformers\TarifTransformer;
use Illuminate\Http\Request;

class TarifController extends ApiController
{
    public function index(Request $request)
    {
        $type = $request->type ?? null;
        if($type){
            $tarifs = Tarif::where('type', $type)->orderBy('lft', 'asc')->get();
            if(count($tarifs) < 1){
                return $this->errorNotFound();
            }
        }else{
            $tarifs = Tarif::orderBy('lft', 'asc')->get();
        }
        return $this->respondWithCollection($tarifs, new TarifTransformer($this->locale));
    }
}