not getting any response from Google Checkout after successfully payment

I am not getting any response by Google Checkout:

I have the sample code from http://code.google.com/p/google-checkout-php-sample-code/downloads/list .

I am using this code in cartdemo.php:

 // Specify <edit-cart-url>
  $cart->SetEditCartUrl("https://mydomain.com/checkout/demo/responsehandlerdemo.php");

  // Specify "Return to xyz" link
  $cart->SetContinueShoppingUrl("https://mydomain.com/checkout/demo/responsehandlerdemo.php");

And I am using following settings:

API callback URL (Level 2 integrations only) [?] Specify a URL for Google to notify you of new orders and changes in order state. [?] API callback URL:
Callback contents: http://mydomain.com/checkout/demo/responsehandlerdemo.php

**Notification Serial Number**

but not getting any response,after completation of payment. I have also changed the settings with "Notification as XML" by using https. actually the application require to integrate simple google checkout functionality.Which will have an checkout button and after successful payment the order history with payment detail will save in my database.

I don't know what is missing. is there any way do implement it simply using 1-2 files not so bulky code?

thanks

Solution

The code you have above doesn't have anything to do with getting data from Google after completion of payment (Notification API).

The code you have above is for the Checkout API which is the flow that involves sending your shopping cart data to Google.

edit-cart-url is the url that is displayed to the customer on checkout if they want to go back to your site instead of placing the order/continuing with the checkout process.
continue-shopping-url is the link presented to the customer to go back to your web site after successful checkout.

You have to implement the Notification API (of which one option is serial number notification) to obtain data from Google. The url to your handler is set in your account (same place where you see the options you mention above).

If you want to see sample PHP code (I'm not a Php dev, am .Net) for a handler that implements serial number notification, see basicapiresponshandlerdemo.php