<?php
use Microsoft\Graph\GraphServiceClient;
use Microsoft\Graph\Generated\Applications\Item\Synchronization\AcquireAccessToken\AcquireAccessTokenPostRequestBody;
use Microsoft\Graph\Generated\Models\SynchronizationSecretKeyStringValuePair;
$graphServiceClient = new GraphServiceClient($tokenRequestContext, $scopes);
$requestBody = new AcquireAccessTokenPostRequestBody();
$credentialsSynchronizationSecretKeyStringValuePair1 = new SynchronizationSecretKeyStringValuePair();
$credentialsSynchronizationSecretKeyStringValuePair1->setOdataType('microsoft.graph.synchronizationSecretKeyStringValuePair');
$credentialsArray []= $credentialsSynchronizationSecretKeyStringValuePair1;
$requestBody->setCredentials($credentialsArray);
$graphServiceClient->applications()->byApplicationId('application-id')->synchronization()->acquireAccessToken()->post($requestBody)->wait();