Google Wallet Postback Blank - android-pay

Question

Solution
The server logs are telling me that I was getting a 301 redirect. This is an .htaccess issue, not GWallet. The redirect was stripping my POST data, leading to a blank request. Thanks everybody for your help.
I'm trying to process the postback from Google Wallet, but I'm not getting the proper data from Google Wallet to start.
Apache's error_log doesn't have any entry for my postback. The access_log shows the following for every attempt at a postback request:
[source-ip-1] - - [16/Sep/2013:15:18:05 +0000] "POST /google-postback.php HTTP/1.1" 301 293 "-" "Google-In-App-Payments; (+http://www.google.com/payments)"
[source-ip-2] - - [16/Sep/2013:15:18:06 +0000] "GET /google-postback.php HTTP/1.1" 200 20 "-" "Google-In-App-Payments; (+http://www.google.com/payments)"
[source-ip-1] - - [16/Sep/2013:15:18:36 +0000] "POST /google-postback.php HTTP/1.1" 301 293 "-" "Google-In-App-Payments; (+http://www.google.com/payments)"
[source-ip-2] - - [16/Sep/2013:15:18:36 +0000] "GET /google-postback.php HTTP/1.1" 200 20 "-" "Google-In-App-Payments; (+http://www.google.com/payments)"
A reverse-DNS shows both IPs are google proxies.
The JavaScript performing the request is as follows:
<script src="https://sandbox.google.com/checkout/inapp/lib/buy.js"></script>
<script type="text/javascript">
//Success handler
var successHandler = function(purchaseAction){
if (window.console != undefined) {
console.log("Purchase completed successfully.");
}
}
//Failure handler
var failureHandler = function(purchaseActionError){
if (window.console != undefined) {
console.log("Purchase did not complete.");
}
}
function purchase()
{
console.log("Attempting to buy stuff");
google.payments.inapp.buy({
'jwt' : '<?=$jwt?>',
'success' : successHandler,
'failure' : failureHandler
});
}
</script>
I POSTed to my postback page myself with the JWT string I giving to Google Wallet's buy() function, and it decodes to what I expected:
stdClass Object
(
[iss] => [my seller id]
[aud] => Google
[typ] => google/payments/inapp/item/v1
[exp] => 1379106326
[iat] => 1379102726
[request] => stdClass Object
(
[name] => Piece of Cake
[decription] => Virtual whazzit
[price] => 10.50
[currencyCode] => USD
[sellerData] => id:1224245,offer_code:3098576987,affiliate:aksdfbovu9j
)
)
Originally, my postback looked like this:
<?php
require_once "google/googlefunctions.php";
$encoded_jwt = $_POST["jwt"];
$decodedJWT = JWT::decode($encoded_jwt, [seller_secret]);
$orderId = $decodedJWT->response->orderId;
header("HTTP/1.0 200 OK");
echo $orderId;
?>
But Google's popup kept returning an error about not being able to verify the purchase (I forget the exact message). After trouble-shooting, I've decided to email myself to verify that I'm actually hitting the postback, and not being blocked by a seller id/secret credentials problem:
// google-postback.php
<?php
mail("my#email.com", "Purchase post", print_r($_POST, true));
?>
My response email is as follows:
Array
(
)
As far as I know, Google Wallet should be sending me a POST with a 'jwt' variable to decode that's identical to what I sent, but with a response, but I'm getting nothing.
Any ideas?