Overview
MongoDB stores data records as BSON documents. BSON is a binary representation of JSON documents, though it contains more data types than JSON. For the BSON spec, see bsonspec.org.
By default, the MongoDB PHP Library returns BSON documents as
MongoDB\Model\BSONDocument objects and BSON arrays as
MongoDB\Model\BSONArray objects, respectively.
Classes
MongoDB\Model\BSONArrayThis class extends PHP's ArrayObject class. It also implements PHP's JsonSerializable interface and the extension's MongoDB\BSON\Serializable and MongoDB\BSON\Unserializable interfaces.
By default, the library will deserialize BSON arrays as instances of this class. During BSON and JSON serialization, instances of this class will serialize as an array type (array_values() is used internally to numerically reindex the array).
MongoDB\Model\BSONDocumentThis class extends PHP's ArrayObject class. It also implements PHP's JsonSerializable interface and the extension's MongoDB\BSON\Serializable and MongoDB\BSON\Unserializable interfaces.
By default, the library will deserialize BSON documents as instances of this class. During BSON and JSON serialization, instances of this class will serialize as a document type (object casting is used internally).