<?php
use Microsoft\Graph\GraphServiceClient;
use Microsoft\Graph\Generated\ServicePrincipals\Item\AddTokenSigningCertificate\AddTokenSigningCertificatePostRequestBody;
$graphServiceClient = new GraphServiceClient($tokenRequestContext, $scopes);
$requestBody = new AddTokenSigningCertificatePostRequestBody();
$requestBody->setDisplayName('CN=customDisplayName');
$requestBody->setEndDateTime(new \DateTime('2024-01-25T00:00:00Z'));
$result = $graphServiceClient->servicePrincipals()->byServicePrincipalId('servicePrincipal-id')->addTokenSigningCertificate()->post($requestBody)->wait();