<?php
use Microsoft\Graph\Beta\GraphServiceClient;
use Microsoft\Graph\Beta\Generated\Directory\Recommendations\Item\Dismiss\DismissPostRequestBody;
$graphServiceClient = new GraphServiceClient($tokenRequestContext, $scopes);
$requestBody = new DismissPostRequestBody();
$requestBody->setDismissReason('Recommendations is not relevant for my organization because...');
$result = $graphServiceClient->directory()->recommendations()->byRecommendationId('recommendation-id')->dismiss()->post($requestBody)->wait();