The MongoDbStore is not compatible with the latest versions of mongodb extension. The latest mongodb extension uses a new way of creating the client. Instead of [`MongoDB\Client`](https://docs.mongodb.com/php-library/v1.6/reference/method/MongoDBClient__construct/) we now have [`MongoDB\Driver\Manager`](https://www.php.net/manual/en/class.mongodb-driver-manager.php). Some options to consider: 1. Make the store work for both interfaces. 2. Migrate the store to the new interface. 3. Create a new MongoDbStore implementation for the latest version of the interface. 4. Use an adapter: https://github.com/alcaeus/mongo-php-adapter. 5. Drop mongodbstore.