(mongodb >=1.4.0)
The MongoDB\Driver\Session class represents a client session and is returned by MongoDB\Driver\Manager::startSession() . Commands, queries, and write operations may then be associated the session.
MongoDB\Driver\Session::TRANSACTION_NONE There is no transaction in progress.
MongoDB\Driver\Session::TRANSACTION_STARTING A transaction has been started, but no operation has been sent to the server.
MongoDB\Driver\Session::TRANSACTION_IN_PROGRESS A transaction is in progress.
MongoDB\Driver\Session::TRANSACTION_COMMITTED The transaction was committed.
MongoDB\Driver\Session::TRANSACTION_ABORTED The transaction was aborted.