Mdb\PayPal\Ipn\ListenerBuilder\ModeDependentServiceEndpoint::getServiceEndpoint PHP Method

    protected function getServiceEndpoint()
    {
        return $this->useSandbox ? 'https://www.sandbox.paypal.com/cgi-bin/webscr' : 'https://ipnpb.paypal.com/cgi-bin/webscr';
    }