如何从PHP向MongoDB写空的关联数组({}) [英] How to write empty associative array ({}) to MongoDB from PHP

问题描述

当我尝试从PHP向MongoDB插入空的关联数组(hashmap/dictionary/dict/{})时，它总是作为非关联的空数组插入(list/[]).我可以强制关联数组吗?

When I try to insert empty associative array (hashmap/dictionary/dict/{}) to MongoDB from PHP, it is always inserted as non-associative empty array (list/[]). Can I force associative array?

示例:

$m = new Mongo('mongodb://localhost:27017');
$db = $m->selectDB('test');
$collection = $db->selectCollection('test');

// 1: inserts []
$d = array( 'x' => array() );
$collection->insert($d);

// 2: inserts []
$d = array( 'y' => array('a'=>'123') );
unset($d['y']['a']);
$collection->insert($d);

// 3: inserts {}
$d = array( 'z' => array('a'=>'123') );
$collection->insert($d);
$collection->update(array('_id' => $d['_id']), array('$unset' => array('z.a'=>true)));

结果:

> db.test.find().pretty()
{ "_id" : ObjectId("510fb9ede695c5381a000000"), "x" : [ ] }
{ "_id" : ObjectId("510fb9ede695c5381a000001"), "y" : [ ] }
{ "_id" : ObjectId("510fb9ede695c5381a000002"), "z" : { } }

第三种方法可以满足我的要求，但是有点尴尬，需要两个查询.有更好的解决方案吗?

The third way does what I want, but it is a bit awkward and requires two queries. Is there a better solution?

推荐答案

无论您存储的是空对象还是数组，都有什么区别?在BSON中，数组和对象的存储方式与字典相同.无论如何，对您的问题.

Whether you store an empty object or array, what's the difference? In BSON, arrays and objects are stored the same way, as a dict. Anyways, to your question.

对于PHP MongoDB驱动程序，一个空数组就是一个空数组，因此将其存储为一个数组.当您将键/值对添加到数组时，驱动程序将其理解为它应该存储对象.

For the PHP MongoDB driver an empty array is just that, an empty array, so it stores it as an array. When you add a key/value pair to the array, that's how the driver understands it should store an object.

如果您真的想存储一个空对象，请尝试:

If you really want to store an empty object, try :

$d = new \stdClass();
$collection->insert(array('z' => $d));

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