curl -H "MicroworkersApiKey:YOUR_API_KEY" -X PUT https://api.microworkers.com/campaign_hg/change_group/<campaign_id> -d "group_id=<group_id>"

<?php

include "includes/RESTClient.php";
define("cAPI_KEY", "YOUR_API_KEY");
define("cAPI_URL", "https://api.microworkers.com");
$client = new RESTClient();
$client->setApiKey(cAPI_KEY);
$client->setUrl(cAPI_URL . "/campaign_hg/change_group/137956568899");
$client->setMethod("PUT");

$client->setData(
array('group_id' => '1111')
);

$client->execute();
$response = $client->getLastResponse();
$client->resetClient();
echo $response;

?>

use MW_API;
use Data::Dumper qw(Dumper);
my $mw_api = MW_API->new('api_key' => 'YOUR_API_KEY');
my $res = $mw_api->do_request('PUT', '/campaign_hg/change_group/137956568899', {
  'group_id' => '1111'
});
print Dumper($res);

from pprint import pprint
from MW_API import MW_API
mw_api = MW_API('YOUR_API_KEY')
res = mw_api.do_request('PUT', '/campaign_hg/change_group/137956568899', {
  'group_id': '1111'
})
pprint(res)

using System;
using MWAPI;
using System.Collections.Specialized;

public class Test
{
  public static void Main (string[] args)
  {
    MW_API MW_API_Client = new MW_API ("YOUR_API_KEY");
    NameValueCollection postData = new NameValueCollection();
    postData.Add("group_id", "1111");
    string body = MW_API_Client.putRequest("/campaign_hg/change_group/137956568899", postData);
    Console.WriteLine (body);
  }
}