oauth2-server/examples/public/refresh_token.php

<?php

use League\OAuth2\Server\Exception\OAuthServerException;
use League\OAuth2\Server\Grant\RefreshTokenGrant;
use League\OAuth2\Server\Server;
use OAuth2ServerExamples\Repositories\AccessTokenRepository;
use OAuth2ServerExamples\Repositories\ClientRepository;
use OAuth2ServerExamples\Repositories\RefreshTokenRepository;
use OAuth2ServerExamples\Repositories\ScopeRepository;
use Slim\App;
use Slim\Http\Request;
use Slim\Http\Response;

include __DIR__.'/../vendor/autoload.php';

// App
$app = new App([Server::class => function () {
    // Init our repositories
    $clientRepository = new ClientRepository();
    $scopeRepository = new ScopeRepository();
    $accessTokenRepository = new AccessTokenRepository();
    $refreshTokenRepository = new RefreshTokenRepository();

    $privateKeyPath = 'file://'.__DIR__.'/../private.key';
    $publicKeyPath = 'file://'.__DIR__.'/../public.key';

    // Setup the authorization server
    $server = new Server(
        $clientRepository,
        $accessTokenRepository,
        $scopeRepository,
        $privateKeyPath,
        $publicKeyPath
    );

    // Enable the refresh token grant on the server
    $server->enableGrantType(new RefreshTokenGrant($refreshTokenRepository), new \DateInterval('PT1H'));

    return $server;
}]);

$app->post('/access_token', function (Request $request, Response $response) {
    /** @var Server $server */
    $server = $this->get(Server::class);
    try {
        return $server->respondToRequest($request, $response);
    } catch (OAuthServerException $e) {
        return $e->generateHttpResponse($response);
    } catch (\Exception $e) {
        return $response->withStatus(500)->write(
            sprintf('<h1>%s</h1><p>%s</p>', get_class($e), $e->getMessage())
        );
    }
});

$app->run();