arg_name: param
name: $key
type: array|object
description: |
  Specifies the field or fields to index and the index order.
  
  For example, the following specifies a descending index
  on the ``username`` field:
  
  .. code-block:: php
  
     $key = [ 'username' => -1 ];

operation: MongoDB\\Collection::createIndex
interface: phpmethod
optional: false
position: 1
---
source:
  file: apiargs-common-param.yaml
  ref: $options
operation: MongoDB\\Collection::createIndex
position: 2
...