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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。

    Table of Contents

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    User Contributed Notes 7 notes

    up
    8
    Lionel
    10 years ago
    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

    ?>
    up
    7
    rmarscher
    11 years ago
    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;
    ?>
    up
    5
    georgedot dont spam me gmail caom
    10 years ago
    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);
            }

        }
    }
    ?>
    up
    2
    Ryan S
    11 years ago
    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);
            }
        }
    ?>
    up
    2
    lensvil dot co at gmail dot com
    7 years ago
    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;
    up
    2
    sararschreiber at gmail dot com
    13 years ago
    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();

    ?>
    up
    2
    alex dot turpin at gmail dot com
    12 years ago
    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
    ?>
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