MongoDB\BSON
PHP Manual

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

MongoDB\BSON\ObjectId
final class MongoDB\BSON\ObjectId implements MongoDB\BSON\ObjectIdInterface, MongoDB\BSON\Type, JsonSerializable, Stringable {
/* Methods */
final public __construct(stringnull $id = null)
final public int getTimestamp()
final public mixed jsonSerialize()
final public string __toString()
}

Changelog

Version Description
PECL mongodb 2.0.0

This class no longer implements the Serializable interface.

PECL mongodb 1.12.0 Implements Stringable for PHP 8.0+.
PECL mongodb 1.3.0

Renamed from MongoDB\BSON\ObjectID to MongoDB\BSON\ObjectId.

Implements MongoDB\BSON\ObjectIdInterface.

PECL mongodb 1.2.0 Implements Serializable and JsonSerializable.

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