test gist

index.php

<?php

use Symfony\Component\HttpFoundation\Request;
use frontend\model\Initializer;

include_once('config.php');
include_once('lib/autoload.php');
include_once('app/bootstrap.php');

$initializer = new Initializer();
$initializer->kernel();
$initializer->doctrine();

$kernel  = $initializer->getKernel();
$request = Request::createFromGlobals();

try {
    $repo    = $initializer->getEntityManager()->getRepository('frontend\model\entity\User');
    $results = $repo->findAll();
    var_dump($results);

    $response = $kernel->handle($request);
    $response->send();

    $kernel->terminate($request, $response);
} catch (Exception $e) {
    //TODO: improve 404 handle
    echo '404: ' . $e->getMessage();
}