Adding subscribers to a list using Mailchimp's API v3

Question

I'm trying to add users to a list I've created in Mailchimp but I can't find any code examples anywhere. I've tried figuring out how to use the API but I'm very much a "Look at an example and learn" kind of person.

I've tried using version 2 of the API but nothing seems to be working despite working from examples on the net and Mailchimp says the following about earlier versions of their API on their website:

Versions 2.0 and earlier are deprecated. Only minimal support—bug fixes, security patches—will be available for those versions.

UPDATE 1: I did some further research based on TooMuchPete's answer with regards to the link on Managing Subscribers and altered some code I found here, but it won't work because the function http_build_query() doesn't deal with nested arrays. I'm not sure how to deal with the 'merge_fields' portion of adding a subscriber. My current code is below:

$postdata = http_build_query(
                    array(
                        'apikey'        => $apikey,
                        'email_address' => $email,
                        'status'        => 'subscribed',
                        'merge_fields'  => array(
                            'FNAME' => $name
                        )
                    )
                );

                $opts = array('http' =>
                    array(
                        'method'  => 'POST',
                        'header'  => 'Content-type: application/x-www-form-urlencoded',
                        'content' => $postdata
                    )
                );

                $context  = stream_context_create($opts);

                $result = file_get_contents('https://us2.api.mailchimp.com/3.0/lists/<list_id>/members/', false, $context);

                var_dump($result);
                die('Mailchimp executed');

UPDATE 2: I've now resorted to using curl and I've managed to get something almost working. The data sends through to Mailchimp but I'm receiving the error "Your request did not include an API key." I'm guessing I need to authenticate as mentioned here. I've tried adding it to the http header which hasn't worked. See my code below:

$apikey = '<api_key>';
                $auth = base64_encode( 'user:'.$apikey );

                $data = array(
                    'apikey'        => $apikey,
                    'email_address' => $email,
                    'status'        => 'subscribed',
                    'merge_fields'  => array(
                        'FNAME' => $name
                    )
                );
                $json_data = json_encode($data);

                $ch = curl_init();
                curl_setopt($ch, CURLOPT_URL, 'https://us2.api.mailchimp.com/3.0/lists/<list_id>/members/');
                curl_setopt($ch, CURLOPT_HTTPHEADER, array('Content-Type: application/json/r/n
                                                            Authorization: Basic '.$auth));
                curl_setopt($ch, CURLOPT_USERAGENT, 'PHP-MCAPI/2.0');
                curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
                curl_setopt($ch, CURLOPT_TIMEOUT, 10);
                curl_setopt($ch, CURLOPT_POST, true);
                curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
                curl_setopt($ch, CURLOPT_POSTFIELDS, $json_data);                                                                                                                  

                $result = curl_exec($ch);

                var_dump($result);
                die('Mailchimp executed');

Answer 1

Based on the List Members Instance docs, the easiest way is to use a PUT request which according to the docs either "adds a new list member or updates the member if the email already exists on the list".

Furthermore apikey is definitely not part of the json schema and there's no point in including it in your json request.

Also, as noted in @TooMuchPete's comment, you can use CURLOPT_USERPWD for basic http auth as illustrated in below.

I'm using the following function to add and update list members. You may need to include a slightly different set of merge_fields depending on your list parameters.

$data = [
    'email'     => '[email protected]',
    'status'    => 'subscribed',
    'firstname' => 'john',
    'lastname'  => 'doe'
];

syncMailchimp($data);

function syncMailchimp($data) {
    $apiKey = 'your api key';
    $listId = 'your list id';

    $memberId = md5(strtolower($data['email']));
    $dataCenter = substr($apiKey,strpos($apiKey,'-')+1);
    $url = 'https://' . $dataCenter . '.api.mailchimp.com/3.0/lists/' . $listId . '/members/' . $memberId;

    $json = json_encode([
        'email_address' => $data['email'],
        'status'        => $data['status'], // "subscribed","unsubscribed","cleaned","pending"
        'merge_fields'  => [
            'FNAME'     => $data['firstname'],
            'LNAME'     => $data['lastname']
        ]
    ]);

    $ch = curl_init($url);

    curl_setopt($ch, CURLOPT_USERPWD, 'user:' . $apiKey);
    curl_setopt($ch, CURLOPT_HTTPHEADER, ['Content-Type: application/json']);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($ch, CURLOPT_TIMEOUT, 10);
    curl_setopt($ch, CURLOPT_CUSTOMREQUEST, 'PUT');
    curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
    curl_setopt($ch, CURLOPT_POSTFIELDS, $json);                                                                                                                 

    $result = curl_exec($ch);
    $httpCode = curl_getinfo($ch, CURLINFO_HTTP_CODE);
    curl_close($ch);

    return $httpCode;
}