GeteBayDetails example.

get_ebay_details.php

<?php
require __DIR__.'/vendor/autoload.php';

use \DTS\eBaySDK\Constants;
use \DTS\eBaySDK\Trading\Services;
use \DTS\eBaySDK\Trading\Types;

$sites = array(
    array('id' => Constants\SiteIds::US, 'name' => 'United States'),
    array('id' => Constants\SiteIds::ENCA, 'name' => 'Canada (English)'),
    array('id' => Constants\SiteIds::GB, 'name' => 'UK'),
    array('id' => Constants\SiteIds::AU, 'name' => 'Australia'),
    array('id' => Constants\SiteIds::AT, 'name' => 'Austria'),
    array('id' => Constants\SiteIds::FRBE, 'name' => 'Belgium (French)'),
    array('id' => Constants\SiteIds::FR, 'name' => 'France'),
    array('id' => Constants\SiteIds::DE, 'name' => 'Germany'),
    array('id' => Constants\SiteIds::MOTORS, 'name' => 'Motors'),
    array('id' => Constants\SiteIds::IT, 'name' => 'Italy'),
    array('id' => Constants\SiteIds::NLBE, 'name' => 'Belgium (Dutch)'),
    array('id' => Constants\SiteIds::NL, 'name' => 'Netherlands'),
    array('id' => Constants\SiteIds::ES, 'name' => 'Spain'),
    array('id' => Constants\SiteIds::CH, 'name' => 'Switzerland'),
    array('id' => Constants\SiteIds::HK, 'name' => 'Hong Kong'),
    array('id' => Constants\SiteIds::IN, 'name' => 'India'),
    array('id' => Constants\SiteIds::IE, 'name' => 'Ireland'),
    array('id' => Constants\SiteIds::MY, 'name' => 'Malaysia'),
    array('id' => Constants\SiteIds::FRCA, 'name' => 'Canada (French)'),
    array('id' => Constants\SiteIds::PH, 'name' => 'Philippones'),
    array('id' => Constants\SiteIds::PL, 'name' => 'Poland'),
    array('id' => Constants\SiteIds::SG, 'name' => 'Singapore'),
);

foreach($sites as $site) {
    getDetails($site);
}

function getDetails($site) 
{
    $service = new Services\TradingService(array(
        'apiVersion' => '881',
        'siteId' => $site['id']
    ));

    $request = new Types\GeteBayDetailsRequestType();

    $request->RequesterCredentials = new Types\CustomSecurityHeaderType();
    $request->RequesterCredentials->eBayAuthToken = '<PRODUCTION AUTH TOKEN>';

    $request->DetailName = array('ShippingCarrierDetails');

    $response = $service->geteBayDetails($request);

    if ($response->Ack !== 'Success') {
        if (isset($response->Errors)) {
            foreach ($response->Errors as $error) {
                printf("Error: %s\n", $error->ShortMessage);
            }
        }
    } else {
      printf("---------------------------\n%s [%s]\n\n", $site['name'], $site['id']);
      if (count($response->ShippingCarrierDetails)) {
          foreach($response->ShippingCarrierDetails as $details) {
              echo $details->ShippingCarrier."\n";
          }
      } else {
          print("No details found\n");
      }
      print("\n---------------------------\n");
    }
}

A small modification makes it work:

$service = new Services\TradingService([
      'authToken'   => $config['production']['authToken'],
      'credentials' => [
         'appId'  => $config['production']['credentials']['appId'],
         'certId' => $config['production']['credentials']['certId'],
         'devId'  => $config['production']['credentials']['devId']
      ],
      'siteId'      => $site['id']
    ]);

Thanks!