<?php
use Microsoft\Graph\Beta\GraphServiceClient;
use Microsoft\Graph\Beta\Generated\Shares\Item\DriveItem\DriveItemRequestBuilderGetRequestConfiguration;
$graphServiceClient = new GraphServiceClient($tokenRequestContext, $scopes);
$requestConfiguration = new DriveItemRequestBuilderGetRequestConfiguration();
$queryParameters = DriveItemRequestBuilderGetRequestConfiguration::createQueryParameters();
$queryParameters->expand = ["children"];
$requestConfiguration->queryParameters = $queryParameters;
$result = $graphServiceClient->shares()->bySharedDriveItemId('sharedDriveItem-id')->driveItem()->get($requestConfiguration)->wait();