Creates a database reference

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# MongoDB::createDBRef

(PECL mongo >=0.9.0)

MongoDB::createDBRef — Creates a database reference

### Description

public array MongoDB::createDBRef ( string `$collection` , mixed `$document_or_id` )

This method is a flexible interface for creating database refrences (see MongoDBRef).

### Parameters

`collection`

  The collection to which the database reference will point.

`document_or_id`

  If an array or object is given, its _id field will be used as the reference ID. If a MongoId or scalar is given, it will be used as the reference ID.

### Return Values

Returns a database reference array.

If an array without an _id field was provided as the document_or_id parameter, `NULL` will be returned.

### Examples

Example #1 MongoDB::createDBRef() example

Example demonstrating how to programatically create a DB reference array from a document.

`<?php
$articles = $db->articles;
$article = array(
'title' => 'Test article',
'description' => 'Test article description'
);
$articles->insert($article);
$ref = $db->createDBRef('articles', $article);
print_r($article);
print_r($ref);
?>`

The above example will output something similar to:

         Array
         (
             [title] => Test article
             [description] => Test article description
             [_id] => MongoId Object
                 (
                 )

         )
         Array
         (
             [$ref] => articles
             [$id] => MongoId Object
                 (
                 )

         )

Now the $ref can be stored on another document and retrieved later with MongoDB::getDBRef() or MongoCollection::getDBRef().

Example #2 MongoDB::createDBRef() example

Example demonstrating how to programatically create a DB reference from just an id.

`<?php
$id = new MongoId('47cc67093475061e3d9536d2');
$ref = $db->createDBRef('articles', $id);
?>`

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MongoDB
PHP Manual