(mongodb >=1.0.0)
MongoDB\Driver\WriteConcern describes the level of
acknowledgement requested from MongoDB for write operations to a standalone
mongod or to replica sets or to sharded clusters. In
sharded clusters, mongos instances will pass the write
concern on to the shards.
MongoDB\Driver\WriteConcern::MAJORITYMajority of all the members in the set; arbiters, non-voting members, passive members, hidden members and delayed members are all included in the definition of majority write concern.