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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 getHostname ( void ) : string

public getInc ( void ) : int

public getPID ( void ) : int

public getTimestamp ( void ) : int

public static isValid ( mixed $value ) : bool

public static __set_state ( array $props ) : MongoId

public __toString ( void ) : string

}

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

User Contributed Notes

lensvil dot co at gmail dot com 20-May-2016 08:10


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 01:51


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 07:29


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 05-Dec-2012 05:46


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 12-Oct-2012 03:11


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 09:15


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 12:23


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();





?>

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MongoId 类

简介

类摘要

Fields

参见

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User Contributed Notes

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