The MongoDB\BSON\ObjectId class

Introduction

BSON type for an » ObjectId. The value consists of 12 bytes, where the first four bytes are a timestamp that reflect the ObjectId's creation. Specifically, the value consists of:

• a 4-byte value representing the seconds since the Unix epoch,
• a 5-byte random number unique to a machine and process, and
• a 3-byte counter, starting with a random value.

In MongoDB, each document stored in a collection requires a unique _id field that acts as a primary key. If an inserted document omits the _id field, the extension automatically generates an ObjectId for the _id field.

Using ObjectIds for the _id field provides the following additional benefits:

• The creation time of the ObjectId may be accessed using the MongoDB\BSON\ObjectId::getTimestamp() method.
• Sorting on an _id field that stores ObjectId values is roughly equivalent to sorting by creation time.

Class synopsis

Changelog