Amazon Pay Authorization Reference ID

I integrated amazon pay into my website and i followed the instructions from Amazon Pay SDK Simple Checkout. Its all working so far, but in the last step the code example shows that i need an authorization reference id.

namespace AmazonPay;

session_start();

// Create the parameters array
$requestParameters = array();

// Refer to GetDetails.php where the Amazon Order Reference ID was set
$requestParameters['amazon_order_reference_id'] = 'AMAZON_ORDER_REFERENCE_ID';

// Confirm the order by making the ConfirmOrderReference API call
$response = $client->confirmOrderReference($requestParameters);

$responsearray['confirm'] = json_decode($response->toJson());

// If the API call was a success make the Authorize API call
if($client->success)
{
$requestParameters['authorization_amount'] = '175.00';
##################################################
############ WHERE DO I GET THIS? ################
$requestParameters['authorization_reference_id'] = 'Your Unique Reference Id';
$requestParameters['seller_authorization_note'] = 'Authorizing payment';
$requestParameters['transaction_timeout'] = 0;

$response = $client->authorize($requestParameters);
$responsearray['authorize'] = json_decode($response->toJson());
}

// If the Authorize API call was a success, make the Capture API call when you are ready to capture             
for the order (for example when the order has been dispatched)
if($client->success)
{
$requestParameters['amazon_authorization_id'] = 'Parse the Authorize Response for this id';
$requestParameters['capture_amount'] = '175.00';
$requestParameters['currency_code'] = 'USD';
$requestParameters['capture_reference_id'] = 'Your Unique Reference Id';

$response = $client->capture($requestParameters);
$responsearray['capture'] = json_decode($response->toJson());
}

// Echo the Json encoded array for the Ajax success
echo json_encode($responsearray);

As shown above the 'authorization_reference_id' needs to be set. But i dont know how to get it. It isnt in my previous response for Setting a new order. Also its not included in the "confirmOrderReference" response. Did i miss something here or is the code sample not complete?

$requestParameters['authorization_reference_id'] = 'Your Unique Reference Id';

Thanks for any help

authorization_reference_id is given by you. It should be unique.

You can used the uniqid builtin function in PHP to generate that. It must be unique for every request.

$requestParameters['authorization_reference_id'] = uniqid();