Amazon MWS PHP Client Library seems incomplete - php

Question

I am trying to develop an application that uses the ListMatchingProducts method.
The end result will be an application that searches for a given product which is already in an internal stock database and present the results to the user so they can select which Amazon product is a correct match for the one in their database.
The PHP Client Library I found is linked here.
I have edited Samples/.config.inc.php correctly (I have removed the comments and redacted the sensitive information):
define('AWS_ACCESS_KEY_ID', '/*REDACTED BUT SET CORRECTLY*/');
define('AWS_SECRET_ACCESS_KEY', '/*REDACTED BUT SET CORRECTLY*/');
define('APPLICATION_NAME', 'STES_MWS_STOCK_SYNC_APP');
define('APPLICATION_VERSION', '0.1');
define ('MERCHANT_ID', '/*REDACTED BUT SET CORRECTLY*/');
define ('MARKETPLACE_ID', 'A1F83G8C2ARO7P'); // Marketplace ID for the UK
I have also uncommented the appropriate line in Samples/ListMatchingProductsSample.php:
$serviceUrl = "https://mws-eu.amazonservices.com/Products/2011-10-01";
Executing this script, however, yeilds the following message (I've redacted some of the XML response):
Caught Exception: Required parameter MarketplaceId not found
Response Status Code: 400
Error Code: MissingParameter
Error Type: Sender
Request ID: /*REDACTED UUID-LIKE STRING*/
XML: <?xml version="1.0"?>
<ErrorResponse xmlns="http://mws.amazonservices.com/schema/Products/2011-10-01"><Error><Type>Sender</Type><Code>MissingParameter</Code><Message>Required parameter MarketplaceId not found</Message><Detail/></Error><RequestID>/*REDACTED UUID-LIKE STRING*/</RequestID></ErrorResponse>
ResponseHeaderMetadata: RequestId: /*REDACTED UUID-LIKE STRING*/, ResponseContext: /*REDACTED LONG STRING*/, Timestamp: 2017-04-24T13:25:33.533Z, Quota Max: 719.0, Quota Remaining: 719.0, Quota Resets At: 2017-04-24T14:03:00.000Z
As this client library has been around since 2011 I find it difficult to believe this is actually incorrect code in the sample, but I can't seem to find where I've gone wrong; scanning through the code I can't find a reference to the MARKETPLACE_ID constant defined in Samples/.config.inc.php
Before I write my own client library (which I had hoped to avoid for such a simple app) I wondered:
Has anyone else had come across this problem and fixed it (and if so, how)?
Is there a newer version of the library I'm not finding?
Can anyone suggest an alternate library if this one really is broken?
-- EDIT --
For completeness, here is the code I am trying to run - the sample code - minus comments:
require_once('.config.inc.php');
$serviceUrl = "https://mws-eu.amazonservices.com/Products/2011-10-01";
$config = array (
'ServiceURL' => $serviceUrl,
'ProxyHost' => null,
'ProxyPort' => -1,
'ProxyUsername' => null,
'ProxyPassword' => null,
'MaxErrorRetry' => 3,
);
$service = new MarketplaceWebServiceProducts_Client(
AWS_ACCESS_KEY_ID,
AWS_SECRET_ACCESS_KEY,
APPLICATION_NAME,
APPLICATION_VERSION,
$config);
$request = new MarketplaceWebServiceProducts_Model_ListMatchingProductsRequest();
$request->setSellerId(MERCHANT_ID);
invokeListMatchingProducts($service, $request);
function invokeListMatchingProducts(MarketplaceWebServiceProducts_Interface $service, $request)
{
try {
$response = $service->ListMatchingProducts($request);
echo ("Service Response\n");
echo ("=============================================================================\n");
$dom = new DOMDocument();
$dom->loadXML($response->toXML());
$dom->preserveWhiteSpace = false;
$dom->formatOutput = true;
echo $dom->saveXML();
echo("ResponseHeaderMetadata: " . $response->getResponseHeaderMetadata() . "\n");
} catch (MarketplaceWebServiceProducts_Exception $ex) {
echo("Caught Exception: " . $ex->getMessage() . "\n");
echo("Response Status Code: " . $ex->getStatusCode() . "\n");
echo("Error Code: " . $ex->getErrorCode() . "\n");
echo("Error Type: " . $ex->getErrorType() . "\n");
echo("Request ID: " . $ex->getRequestId() . "\n");
echo("XML: " . $ex->getXML() . "\n");
echo("ResponseHeaderMetadata: " . $ex->getResponseHeaderMetadata() . "\n");
}
}

Answer 1

Frankly it seems like the "samples" are a bit naff.
Looking at the code, it seems likely you need to set the marketplaceId manually, either in the constructor via an associative array or as a setter method call.
e.g.
$request->setMarketplaceId(MARKETPLACE_ID)