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 ;

public __construct ([ string $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。

MongoId::__construct — 创建一个新的id
MongoId::getHostname — 获取这台机器上 id 所使用的 hostname
MongoId::getInc — 返回用于创建 id 所增加的值
MongoId::getPID — 获取进程 ID
MongoId::getTimestamp — 获取新纪元时间到 id 创建时的秒数。
MongoId::isValid — Check if a value is a valid ObjectId
MongoId::__set_state — 创建一个假的 MongoId
MongoId::__toString — 返回该 id 十六进制的表示形式

用户评论:

[#1] Lionel [2013-07-08 01:51:36]

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 ?>

[#2] georgedot dont spam me gmail caom [2013-07-03 07:29:43]

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); } } } ?>

[#3] Ryan S [2012-12-05 17:46:53]

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);         }     } ?>

[#4] rmarscher [2012-10-12 15:11:16]

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; ?>

[#5] alex dot turpin at gmail dot com [2011-07-11 09:15:34]

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 ?>

[#6] sararschreiber at gmail dot com [2010-10-12 12:23:25]

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(); ?>

MongoId 类

简介

类摘要

Fields

参见

Table of Contents

用户评论: