// Start PHP session
session_start();

$app = new \Slim\App();

// Register with container
$container = $app->getContainer();
$container['csrf'] = function ($c) {
    return new \Slim\Csrf\Guard;
};

// Register middleware
$app->add($container->get('csrf'));

$app->get('/foo', function ($req, $res, $args) {
    // CSRF token name and value
    $nameKey = $this->csrf->getTokenNameKey();
    $valueKey = $this->csrf->getTokenValueKey();
    $name = $req->getAttribute($nameKey);
    $value = $req->getAttribute($valueKey);

    // Render HTML form which POSTs to /bar with two hidden input fields for the
    // name and value:
    // <input type="hidden" name="<?= $nameKey ?>" value="<?= $name ?>">
    // <input type="hidden" name="<?= $valueKey ?>" value="<?= $value ?>">
});

$app->post('/bar', function ($req, $res, $args) {
    // CSRF protection successful if you reached
    // this far.
});

$app->run();

$container['csrf'] = function ($c) {
    $guard = new \Slim\Csrf\Guard();
    $guard->setFailureCallable(function ($request, $response, $next) {
        $request = $request->withAttribute("csrf_status", false);
        return $next($request, $response);
    });
    return $guard;
};

if (false === $request->getAttribute('csrf_status')) {
    // display suitable error here
} else {
    // successfully passed CSRF check
}