fkooman\OAuth\Client\SessionStorage::storeRefreshToken PHP Method

    public function storeRefreshToken(RefreshToken $refreshToken)
    {
        if (!isset($_SESSION['php-oauth-client']['refresh_token'])) {
            $_SESSION['php-oauth-client']['refresh_token'] = array();
        }
        array_push($_SESSION['php-oauth-client']['refresh_token'], serialize($refreshToken));
        return true;
    }