I struggled for awhile to identify the way to find() using a ObjectID This seems to work, I hope this helps someone else out. $mongoId = '5a2493c33c95a1281836eb6a';$collection->find(['_id'=> new MongoDB\BSON\ObjectId("$mongoId")]);I found it here: https://docs.mongodb.com/php-library/current/reference/method/MongoDBCollection-findOne/Note this is for the PHP library, not the legacy library.