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<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision$ -->
<reference xml:id="class.mongodb-bson-objectid" role="class" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude">
<title>The MongoDB\BSON\ObjectId class</title>
<titleabbrev>MongoDB\BSON\ObjectId</titleabbrev>
<partintro>
<!-- {{{ MongoDB\BSON\ObjectId intro -->
<section xml:id="mongodb-bson-objectid.intro">
&reftitle.intro;
<para>
BSON type for an
<link xlink:href="&url.mongodb.docs.bson;#objectid">ObjectId</link>. 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:
</para>
<itemizedlist>
<listitem><simpara>a 4-byte value representing the seconds since the Unix epoch,</simpara></listitem>
<listitem><simpara>a 5-byte random number unique to a machine and process, and</simpara></listitem>
<listitem><simpara>a 3-byte counter, starting with a random value.</simpara></listitem>
</itemizedlist>
<para>
In MongoDB, each document stored in a collection requires a unique
<literal>_id</literal> field that acts as a primary key. If an inserted
document omits the <literal>_id</literal> field, the extension automatically
generates an ObjectId for the <literal>_id</literal> field.
</para>
<para>
Using ObjectIds for the <literal>_id</literal> field provides the following
additional benefits:
</para>
<itemizedlist>
<listitem><simpara>The creation time of the ObjectId may be accessed using the <methodname>MongoDB\BSON\ObjectId::getTimestamp</methodname> method.</simpara></listitem>
<listitem><simpara>Sorting on an <literal>_id</literal> field that stores ObjectId values is roughly equivalent to sorting by creation time.</simpara></listitem>
</itemizedlist>
</section>
<!-- }}} -->
<section xml:id="mongodb-bson-objectid.synopsis">
&reftitle.classsynopsis;
<!-- {{{ Synopsis -->
<classsynopsis>
<ooclass><classname>MongoDB\BSON\ObjectId</classname></ooclass>
<!-- {{{ Class synopsis -->
<classsynopsisinfo>
<modifier>final</modifier>
<ooclass>
<classname>MongoDB\BSON\ObjectId</classname>
</ooclass>
<oointerface>
<interfacename>MongoDB\BSON\ObjectIdInterface</interfacename>
</oointerface>
<oointerface>
<interfacename>MongoDB\BSON\Type</interfacename>
</oointerface>
<oointerface>
<interfacename>Serializable</interfacename>
</oointerface>
<oointerface>
<interfacename>JsonSerializable</interfacename>
</oointerface>
<oointerface>
<interfacename>Stringable</interfacename>
</oointerface>
</classsynopsisinfo>
<!-- }}} -->
<classsynopsisinfo role="comment">&Methods;</classsynopsisinfo>
<xi:include xpointer="xmlns(db=http://docbook.org/ns/docbook) xpointer(id('class.mongodb-bson-objectid')/db:refentry/db:refsect1[@role='description']/descendant::db:methodsynopsis[not(@role='procedural')])" />
</classsynopsis>
<!-- }}} -->
</section>
<section role="changelog">
&reftitle.changelog;
<para>
<informaltable>
<tgroup cols="2">
<thead>
<row>
<entry>&Version;</entry>
<entry>&Description;</entry>
</row>
</thead>
<tbody>
<row>
<entry>PECL mongodb 1.12.0</entry>
<entry>
Implements <interfacename>Stringable</interfacename> for PHP 8.0+.
</entry>
</row>
<row>
<entry>PECL mongodb 1.3.0</entry>
<entry>
<para>
Renamed from <literal>MongoDB\BSON\ObjectID</literal> to
<literal>MongoDB\BSON\ObjectId</literal>.
</para>
<para>
Implements <interfacename>MongoDB\BSON\ObjectIdInterface</interfacename>.
</para>
</entry>
</row>
<row>
<entry>PECL mongodb 1.2.0</entry>
<entry>
Implements <interfacename>Serializable</interfacename> and
<interfacename>JsonSerializable</interfacename>.
</entry>
</row>
</tbody>
</tgroup>
</informaltable>
</para>
</section>
</partintro>
&reference.mongodb.bson.entities.objectid;
</reference>
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