Campaignmonitor: How do I update a multi-options (select many) field using PHP wrapper

This question refers to CampaignMonitor API PHP wrapper, function subscriberAddWithCustomFields().

In the CampaignMonitor back-end I created a custom multi-option (select many) field called 'Subscribedto' where the user can select (checkbox) which newsletter he likes to receive: 'News & Updates' and/or开发者_JS百科 'News from Partners'. Now I would like to update this field using the PHP API wrapper but can't figure out how to do this.

From my database:

'News & Updates' can be either 0 or 1

'News from Partners' can be either 0 or 1

The following does not work:

$extras = array('Subscribedto'=>array("News & Updates"=>0,"News from Partners"=>1));
$cm_res = $cm->subscriberAddWithCustomFields($email,$name, $extras);

Their new v3 API makes this a lot easier. See http://www.campaignmonitor.com/forums/viewtopic.php?id=5166 in their forums for an answer.

Here's some sample code from one of my forms:

$wrap = new CS_REST_Subscribers($list_id, $api_key);
        $result = $wrap->add(array(
            'EmailAddress' => $email,
            'Name' => '',
            'CustomFields' => array(
                array(
                    'Key' => 'Events',
                    'Value' => 'Event 1'
                )
            ),
            'Resubscribe' => true
        ));

        //echo "Result of POST /api/v3/subscribers/{list id}.{format}\n<br />";
        if($result->was_successful()) {
            $success = true;
            $message = 'Cool!  We\'ll be in touch soon.';
        } else {
            $message = $result->response;
        }