phpvms/app/Http/Requests/CreateFareRequest.php

<?php

namespace App\Http\Requests;

use App\Contracts\FormRequest;
use App\Models\Fare;

class CreateFareRequest extends FormRequest
{
    /**
     * Get the validation rules that apply to the request.
     *
     * @return array
     */
    public function rules(): array
    {
        $rules = Fare::$rules;
        $rules['code'] .= '|unique:fares';
        return $rules;
    }
}