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

     [ 'username' => -1 ]
interface: phpmethod
operation: ~
optional: false
---
source:
  file: apiargs-common-param.yaml
  ref: $options
...
