public function authorizationCodeUrl()
    {
        // Get the Discovery URI
        if (!$this->endpointDiscovery()) return false;

        $url = $this->authorization_endpoint;
        $url .= '?response_type=code';
        $url .= '&client_id=' . $this->mpClientId;
        $url .= '&scope=' . $this->scope . ' openid';
        $url .= '&redirect_uri=' . $this->mpRedirectURL;

        return $url;
    }