I am planning to integrate a Google Checkout payment system on a social networking website. The idea is that members can buy "tokens" for real money (which are sort of the website currency) and then they can buy access to some extra content on the website etc.

What I want to do is create a Google Checkout button that takes a member to the checkout page where he pays with his credit or debit card. What I want is the Google Checkout to notify notify my server whether the purchase of tokens was successful (if the credit/debit card was charged) so I can update the local database.

The website is coded in PHP/MySQL.

I have downloaded the sample PHP code from here: code.google.com/p/google-checkout-php-sample-code/wiki/Documentation

I know how to create a Google checkout button and I have also placed the responsehandlerdemo.php file on my server. This is the file the Google Checkout is supposed to send response to (of course I set the path to the file in Google merchant account).

Now in the response handler file there is a switch block with several case statements. Which one means that the payment was successful and I can add tokens to the member account in the local database?

  switch ($root) {
case "request-received": {
  break;
}
case "error": {
  break;
}
case "diagnosis": {
  break;
}
case "checkout-redirect": {
  break;
}
case "merchant-calculation-callback": {
  // Create the results and send it
  $merchant_calc = new GoogleMerchantCalculations($currency);

  // Loop through the list of address ids from the callback
  $addresses = get_arr_result($data[$root]['calculate']['addresses']['anonymous-address']);
  foreach($addresses as $curr_address) {
    $curr_id = $curr_address['id'];
    $country = $curr_address['country-code']['VALUE'];
    $city = $curr_address['city']['VALUE'];
    $region = $curr_address['region']['VALUE'];
    $postal_code = $curr_address['postal-code']['VALUE'];

    // Loop through each shipping method if merchant-calculated shipping
    // support is to be provided
    if(isset($data[$root]['calculate']['shipping'])) {
      $shipping = get_arr_result($data[$root]['calculate']['shipping']['method']);
      foreach($shipping as $curr_ship) {
        $name = $curr_ship['name'];
        //Compute the price for this shipping method and address id
        $price = 12; // Modify this to get the actual price
        $shippable = "true"; // Modify this as required
        $merchant_result = new GoogleResult($curr_id);
        $merchant_result->SetShippingDetails($name, $price, $shippable);

        if($data[$root]['calculate']['tax']['VALUE'] == "true") {
          //Compute tax for this address id and shipping type
          $amount = 15; // Modify this to the actual tax value
          $merchant_result->SetTaxDetails($amount);
        }

        if(isset($data[$root]['calculate']['merchant-code-strings']
            ['merchant-code-string'])) {
          $codes = get_arr_result($data[$root]['calculate']['merchant-code-strings']
              ['merchant-code-string']);
          foreach($codes as $curr_code) {
            //Update this data as required to set whether the coupon is valid, the code and the amount
            $coupons = new GoogleCoupons("true", $curr_code['code'], 5, "test2");
            $merchant_result->AddCoupons($coupons);
          }
         }
         $merchant_calc->AddResult($merchant_result);
      }
    } else {
      $merchant_result = new GoogleResult($curr_id);
      if($data[$root]['calculate']['tax']['VALUE'] == "true") {
        //Compute tax for this address id and shipping type
        $amount = 15; // Modify this to the actual tax value
        $merchant_result->SetTaxDetails($amount);
      }
      $codes = get_arr_result($data[$root]['calculate']['merchant-code-strings']
          ['merchant-code-string']);
      foreach($codes as $curr_code) {
        //Update this data as required to set whether the coupon is valid, the code and the amount
        $coupons = new GoogleCoupons("true", $curr_code['code'], 5, "test2");
        $merchant_result->AddCoupons($coupons);
      }
      $merchant_calc->AddResult($merchant_result);
    }
  }
  $Gresponse->ProcessMerchantCalculations($merchant_calc);
  break;
}
case "new-order-notification": {
  $Gresponse->SendAck();
  break;
}
case "order-state-change-notification": {
  $Gresponse->SendAck();
  $new_financial_state = $data[$root]['new-financial-order-state']['VALUE'];
  $new_fulfillment_order = $data[$root]['new-fulfillment-order-state']['VALUE'];

  switch($new_financial_state) {
    case 'REVIEWING': {
      break;
    }
    case 'CHARGEABLE': {
      //$Grequest->SendProcessOrder($data[$root]['google-order-number']['VALUE']);
      //$Grequest->SendChargeOrder($data[$root]['google-order-number']['VALUE'],'');
      break;
    }
    case 'CHARGING': {
      break;
    }
    case 'CHARGED': {
      break;
    }
    case 'PAYMENT_DECLINED': {
      break;
    }
    case 'CANCELLED': {
      break;
    }
    case 'CANCELLED_BY_GOOGLE': {
      //$Grequest->SendBuyerMessage($data[$root]['google-order-number']['VALUE'],
      //    "Sorry, your order is cancelled by Google", true);
      break;
    }
    default:
      break;
  }

  switch($new_fulfillment_order) {
    case 'NEW': {
      break;
    }
    case 'PROCESSING': {
      break;
    }
    case 'DELIVERED': {
      break;
    }
    case 'WILL_NOT_DELIVER': {
      break;
    }
    default:
      break;
  }
  break;
}
case "charge-amount-notification": {
  //$Grequest->SendDeliverOrder($data[$root]['google-order-number']['VALUE'],
  //    <carrier>, <tracking-number>, <send-email>);
  //$Grequest->SendArchiveOrder($data[$root]['google-order-number']['VALUE'] );
  $Gresponse->SendAck();
  break;
}
case "chargeback-amount-notification": {
  $Gresponse->SendAck();
  break;
}
case "refund-amount-notification": {
  $Gresponse->SendAck();
  break;
}
case "risk-information-notification": {
  $Gresponse->SendAck();
  break;
}
default:
  $Gresponse->SendBadRequestStatus("Invalid or not supported Message");
  break;

}

I guess that case 'CHARGED' is the one, am I right?

Second question, do I need an SSL certificate to receive response from Google Checkout? According to this I do: groups.google.com/group/google-checkout-api-php/browse_thread/thread/10ce55177281c2b0

But I don's see it mentioned anywhere in the official documentation.

Thank you.