How do I pull the subscriber count from a MailChimp list with the API?

I'm trying to display the subscriber count from a MailChimp mailing list using their API, and I've got it partially working, except the code below is currently spitting out the subscriber count for all lists, rather than for one specific list. I've specified the list id in the line $listId ='XXX'; but that doesn't seem to be working. Because I have five lists in total, the output from the PHP below shows this:

10 0 0 1 9

What do I need to do in my code below to get the subscriber count from a specific list id?

<?php
/**
This Example shows how to pull the Members of a List using the MCAPI.php 
class and do some basic error checking.
**/
require_once 'inc/MCAPI.class.php';

$api开发者_高级运维key = 'XXX';
$listId = 'XXX';

$api = new MCAPI($apikey);

$retval = $api->lists();

if ($api->errorCode){
    echo "Unable to load lists()!";
    echo "\n\tCode=".$api->errorCode;
    echo "\n\tMsg=".$api->errorMessage."\n";
} else {
    foreach ($retval['data'] as $list){
        echo "\t ".$list['stats']['member_count'];
    }
}

?>

I just came across this function (see below) that let's me return a single list using a known list_id. The problem is, I'm not sure how to add the list_id in the function.

I'm assuming I need to define it in this line? $params["filters"] = $filters;

The MailChimp lists() method documentation can be referred to here: http://apidocs.mailchimp.com/rtfm/lists.func.php

    function lists($filters=array (
), $start=0, $limit=25) {
        $params = array();
        $params["filters"] = $filters;
        $params["start"] = $start;
        $params["limit"] = $limit;
        return $this->callServer("lists", $params);
    }

I'd strongly recommend not mucking with the internals of the wrapper as it's not going to be nearly as helpful as the online documentation and the examples included with the wrapper. Using the wrapper means the line you tracked down will effectively be filled when make the proper call.

Anywho, this is what you want:

$filters = array('list_id'=>'XXXX');
$lists = $api->lists($filters);

Mailchimp provides a pre-built php wrapper around their api at http://apidocs.mailchimp.com/downloads/#php. This api includes a function lists() which, according to its documentation, returns among other things:

int member_count The number of active members in the given list.

It looks like this is the function which you are referring to above. All you should have to do is iterate through the lists that are returned to find the one with the proper id. From there you should be able to query the subscriber count along with a number of other statistics about the list.