<?php
use Microsoft\Graph\GraphServiceClient;
use Microsoft\Graph\Generated\Models\CustomSecurityAttributeDefinition;
$graphServiceClient = new GraphServiceClient($tokenRequestContext, $scopes);
$requestBody = new CustomSecurityAttributeDefinition();
$requestBody->setAttributeSet('Engineering');
$requestBody->setDescription('Active projects for user');
$requestBody->setIsCollection(true);
$requestBody->setIsSearchable(true);
$requestBody->setName('Project');
$requestBody->setStatus('Available');
$requestBody->setType('String');
$requestBody->setUsePreDefinedValuesOnly(true);
$result = $graphServiceClient->directory()->customSecurityAttributeDefinitions()->post($requestBody)->wait();