Simple Joomla 3 external script with JSON result from database

joomla.php

<?php
defined('_JEXEC') or die('Restricted access');
define('DS', DIRECTORY_SEPARATOR);

// Use these variables for direct file access
// define('_JEXEC', 1);
// define('JPATH_BASE', realpath(dirname(__FILE__)));

require_once (JPATH_BASE.DS.'includes'.DS.'defines.php');
require_once (JPATH_BASE.DS.'includes'.DS.'framework.php');

$app = JFactory::getApplication('site');
$db = JFactory::getDbo();

$jinput = JFactory::getApplication()->input;
$region = $jinput->get('region', 'Abruzzo', 'STRING');

$query = $db->getQuery(true);
$query
    ->select($db->qn('id'))
    ->from($db->qn('#__ambulatori_regioni'))
    ->where($db->qn('nome').' = '.$db->q($region));

$db->setQuery($query);
$result = $db->loadResult();

echo json_encode($result);
?>