PDO does not return any response

I’m using Slim framework for develop a Restful API. I configured the Framework dependencies in this way:

<?php

$container = $app->getContainer();

$container['db'] = function($config)
{
    $db = $config['db'];
    $pdo = new PDO('mysql:host=' . $db['host'] . ';port=' . $db['port'] . ';dbname=' . $db['dbname'], $db['user'], $db['pass']);
    $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    $pdo->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_ASSOC);
    return $pdo;
};

this file is called from index.php which contains the following structure:

<?php

use \Psr\Http\Message\ServerRequestInterface as Request;
use \Psr\Http\Message\ResponseInterface as Response;

require('vendor/autoload.php');

$settings = require __DIR__ . '/src/settings.php';
$app = new \Slim\App($settings);

require __DIR__ . '/src/dependencies.php';

require __DIR__ . '/src/routes.php';

$app->run();

I read the database configuration from settings.php, which return an array that have the following content:

return [
  'settings' =>
  [    
    //Configurazione database.
    'db' =>
    [
      'port' => 3306,
      'host' => 'localhost',
      'dbname' => 'mydb',
      'user' => 'root',
      'pass' => 'root',
    ],
  ],
];

inside the routes.php I defined a simple method that return all the countries available:

<?php

use Slim\Http\Request;
use Slim\Http\Response;

$app->get('/get_countries', function (Request $request, Response $response, array $args)
{
    $sth = $this->db->query("SELECT * FROM country");
    $countries = $sth->fetchAll(PDO::FETCH_OBJ);
    echo json_encode($countries);
});

my request is done as: http://localhost:8081/swp/get_countries

but will return:

if I write only echo "test" inside get_countries all working well, what is wrong?

you can download my project here: https://files.fm/u/5ww8c4be

Hello @serdam

Just a tip: Never use echo in Slim. Please use and return the $response object instead.

Example:

$statement = $this->db->query("SELECT * FROM country");
$countries = $statement->fetchAll(PDO::FETCH_ASSOC);

return $response->withJson($countries);