laravel custom validation

appserviceprovider

public function boot()
    {
        Validator::extend('both_not_filled', function ($attribute, $value, $parameters) {
            $other = $parameters[0];
            if (!empty($value) && !empty($other)) {
                return false;
            }

            return true;
        });
    }

validation rule

'foo' => 'both_not_filled:',$request->get('bar')