(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.