How to get contacts in children of a parent group using the API

Question

I have a child groups C and B, each with 20 different contacts in them. Both child groups are in parent group A. I need to find all contacts in all children of A since C and B might be removed later or new children added to A. But A will not change. However, Group A is not itself populated. As a result, the CiviCRM API returns 0 results. Is there handy API method which will help me out?

API Command:

 $result = civicrm_api3('GroupContact', 'get', array(
  'sequential' => 1,
  'group_id' => "Donors_74",
));

Actual results from the API explorer:

{
"is_error": 0,
"version": 3,
"count": 0,
"values": [

    ]
}

Expected result: 1676

We are using CiviCRM 4.7.25.

Answer 1

You can use the 'group' filter on the Contact api to get members of parent groups.

$result = civicrm_api3('Contact', 'get', array(
  'sequential' => 1,
  'group' => XX,
  'options' => array('limit' => 0),
));

where XX is the id of the parent group (A).

Answer 2

The query worked fine for me, i am using name of group instead of id. Example:

$result = civicrm_api3('Contact', 'get', array(
  'sequential' => 1,
  'group' => "Advisory Board",
  'options' => array('limit' => 0),
));