php-doc-en/reference/mongodb/bson/objectid.xml

<?xml version="1.0" encoding="utf-8"?>
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<phpdoc:classref xml:id="class.mongodb-bson-objectid" xmlns:phpdoc="http://php.net/ns/phpdoc" 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 driver 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>
    </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 1.3.0</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;

</phpdoc:classref>

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