<?php
use Microsoft\Graph\Beta\GraphServiceClient;
use Microsoft\Graph\Beta\Generated\Models\WorkbookComment;
$graphServiceClient = new GraphServiceClient($tokenRequestContext, $scopes);
$requestBody = new WorkbookComment();
$requestBody->setCellAddress('Sheet1!A1');
$requestBody->setContent('This is my comment.');
$requestBody->setContentType('plain');
$result = $graphServiceClient->drives()->byDriveId('drive-id')->items()->byDriveItemId('driveItem-id')->workbook()->comments()->post($requestBody)->wait();