MongoId 类

(PECL mongo >=0.8.0)

简介

为数据库对象创建的唯一标识符。 如果插入数据库的对象不具有 _id 字段，将会为 _id 字段添加一个 MongoId 实例作为值。 如果数据具有自然的唯一字段（比如说，用户名或 timestamp），用来作为 _id 字段也不错，它不会被 一个 MongoId 替换。

MongoId 类实例满足了关系数据库中自增列的角色： 如果数据不具有天然的唯一键，则提供一个。 自增列在分布式数据库中不会工作得很好，因为它无法快速找到下一个数字。 这个类能够满足在分布式下快速产生唯一值的条件。

每个 MongoId 具有 12 个字节（使它的字符串形式是 24 个十六进制字符）。 前四个字节是一个时间戳（timestamp），后三个是客户端主机名的 hash 摘要，然后两个是运行脚本的进程 ID， 最后三位是一个自增值。

MongoId 是可以序列化/反序列化的。 它们序列化后的格式和它们的字符串格式比较像： 

C:7:"MongoId":24:{4af9f23d8ead0e1d32000000}

类摘要

MongoId {
public string $id = NULL ;
/* 方法 */
public __construct ([ string|MongoId $id = NULL ] )
public static string getHostname ( void )
public int getInc ( void )
public int getPID ( void )
public int getTimestamp ( void )
public static bool isValid ( mixed $value )
public static MongoId __set_state ( array $props )
public string __toString ( void )
}

Fields

id
这个字段包含了该对象的字符串表达形式。

参见

关于 » ids 的 MongoDB 核心文档。

Table of Contents

User Contributed Notes

lensvil dot co at gmail dot com 20-May-2016 05:10
Get ObjectId MongoDB via PHP

var_dump($object);

object(MongoDB\Model\BSONDocument)#36 (1) {
  ["storage":"ArrayObject":private]=>
  array(8) {
    ["_id"]=>
    object(MongoDB\BSON\ObjectID)#33 (1) {
      ["oid"]=>
      string(24) "573e69e78fccd968aa066611"
    }
    ["dummy"]=>
    string(5) "mongo"
  }
}

Failure
var_dump($object->_id->oid);
>>> null

var_dump($object->_id->{'oid'});
>>> null

var_dump($object->_id->{'$oid'});
>>> null

Success
$bson = \MongoDB\BSON\fromPHP($object);
$json = \MongoDB\BSON\toJSON($bson);
$result = json_decode($json, true);

var_dump($result['_id']['$oid']);
>>> string(24) "573e69e78fccd968aa066611"
exit;
Lionel 08-Jul-2013 10:51
Just to be careful with the strict comparison. Object inequalities holds.

<?php

$m1 = new MongoId('51b14c2de8e185801f000006');
$m2 = new MongoId('51b14c2de8e185801f000006');

var_dump($m1 === $m2); //gives you boolean false
var_dump($m1 == $m2); //gives you boolean true

$m3 = new MongoId('51b14c2de8e185801f000006');
$m4 = new MongoId('51b14c2de8e185801f000007');

var_dump($m3 === $m4); //gives you boolean false
var_dump($m3 == $m4); //gives you boolean false

?>
georgedot dont spam me gmail caom 03-Jul-2013 04:29
Due to Recent changes.

* [PHP-554] - MongoId should not get constructed when passing in an invalid ID.

Constructor will throw an exception when passing invalid ID.

<?php

$_id = new MongoId(); //Generates new ID
$_id = new MongoId(null); //Generates new ID

$_id = new MongoId("invalid id"); //throws MongoException

?>

<?php
//Revert to old behaviour
$_id = "invalid id";
try {
    $_id = new MongoId($_id);
} catch (MongoException $ex) {
    $_id = new MongoId();
}
?>

<?php
//Nifty hack
class SafeMongoId extends MongoId {

    public function __construct($id=null) {

        try {
            parent::__construct($id);
        } catch (MongoException $ex) {
            parent::__construct(null);
        }

    }
}
?>
Ryan S 06-Dec-2012 02:46
it is important to note that

<?php
    array("_id" => new MongoId("50cf7d2841d41f4f35000000"))
//                   ≠
    array("_id" => array("$id" => "50cf7d2841d41f4f35000000"))
?>

This issue can arrise when using json_encode() and json_decode(). If not paying close enough attention one can assume due to the encoded value of the object that it is just this simple:

<?php
    $item = $db->myCollection->findOne();
    print json_encode($item);
    // {"_id": {"$id": "50cf7d2841d41f4f35000000"}}
    $item = $db->myCollection->findOne(json_encode($item));
    // $item is empty aka not found
?>

Simple solution to handle these situations:

<?php
    class MongoId2 extends MongoId {
        public function __construct($id = null) {
            if(is_array($id)) {
                $id = (object) $id;
            }

            if(is_object($id) && isset($id->{'$id'})) {
                $id = $id->{'$id'};
            }

            return parent::__construct($id);
        }
    }
?>
rmarscher 13-Oct-2012 12:11
You can also cast the id to a string rather than access the $id property to get a string representation of the MongoId.

<?php
$stringId = (string) $mongoId;
?>
alex dot turpin at gmail dot com 11-Jul-2011 06:15
If you need to get the actual ID string, and you try the usual way, PHP will whine because it starts with a dollar sign and it thinks it's a variable. Instead, use this notation:

<?php
    $mongoid->{'$id'} //Get the $id property of a MongoId object
?>
sararschreiber at gmail dot com 12-Oct-2010 09:23
this is useful for querying for an object by id, given the id's hex:

<?php
$userid = '4cb4ab6d7addf98506010000';

$theObjId = new MongoId($userid);

$connection = new Mongo();
$db = $connection->thedb->users;

// this will return our matching entry.
$item = $db->findOne(array("_id" => $theObjId));

$connection->close();

?>