oauth2.php

<?php

class OauthCbController extends AbstractController
{
    /**
     * @Inject("SocialConnect\Auth\Service")
     *
     * @var \SocialConnect\Auth\Service
     */
    protected $oauth;

    public function getAction()
    {
        $id = $this->request->attributes->get('id');
        if ($id) {
            throw new InvalidParameterException('id');
        }

        $provider = $this->oauth->getProvider($id);

        // Access token, access token is needed to perform API requests
        $accessToken = $provider->getAccessTokenByRequestParameters($this->request->query->all());

        $externalUserId = $accessToken->getUserId();
        if ($externalUserId) {
            // some APIs provide us user_id inside AccessToken, for example we can check in db that user have
            // account and skip next step
            return;
        }

        // We get user from social network
        $user = $provider->getIdentity($accessToken);
        
        // check in db that user register inside your site before, or register new account for him
    }
}