API / Notifications s2_signup_notification Webhook

I am trying to code an API / Notification webhook for Signup Notifications. I found the excellent knowledge base article written at https://s2member.com/kb-article/building-an-api-notification-handler-webhook/

That example shows you how to fire a webhook for Payment Notifications using the API

The issue I’m running into is I cannot seem to find the trigger for a Signup Notification.

In the example webhook the variable s2_payment_notification is tested to see if its equal to yes

I’ve tried using s2_signup_notification in its place, but it seems that s2_signup_notification may not be a valid variable.

If one was to want to write a custom webhook for Signup Notification or any other API Notification OTHER THAN payment notifications, what $GET variable would you target?

I’ve search the knowledgebase and I’ve not turned up anything. I tried searching the GitHub repo and I’ve found nothing related to s2_signup_notification anywhere. I’m at a loss for what variable to use.

Here is the code I used while trying to fire a Signup Notification webhook

<?php
add_action('init', 's2_signup_notification');
function s2_signup_notification()
{
    if(!empty($_GET['s2_signup_notification']) && $_GET['s2_signup_notification'] === 'yes')
        // ↑ In my URL, I have <code>?s2_signup_notification=true</code>, that's what I'm looking for here.
    {
        if(!empty($_GET['user_id']) && !empty($_GET['item_number']))
        // In my URL, I have <code>&user_id=%%user_id%%&item_number=%%item_number%%</code>, that's what I'm looking for here.
        {
            $user_id     = (integer)$_GET['user_id']; // I'm expecting an integer in this value.
            $item_number = (string)$_GET['item_number']; // I'm expecting a string in this value.

            $user = new WP_User($user_id); // Get a WordPress User object instance so I can work with this customer.

            // Here I might perform any number of tasks related to this user. Such as creating a user option value in WordPress.
            //update_user_option($user_id, 'my_custom_data_for_this_user', $item_number);

            // I could also collect details about this user, by accessing properties of my WP_User object instance.
            $first_name = $user->first_name;
            $last_name  = $user->last_name;
            $email      = $user->user_email;
            $username   = $user->user_login;

            // I can also pull s2Member option values related to this user.
            $s2member_subscr_id                = get_user_option('s2member_subscr_id', $user_id);
            $s2member_custom_fields            = get_user_option('s2member_custom_fields', $user_id);
            $s2member_custom                   = get_user_option('s2member_custom', $user_id);
            $s2member_registration_ip          = get_user_option('s2member_registration_ip', $user_id);
            $s2member_paid_registration_times  = get_user_option('s2member_paid_registration_times', $user_id);
            $s2member_first_payment_txn_id     = get_user_option('s2member_first_payment_txn_id', $user_id);
            $s2member_last_payment_time        = get_user_option('s2member_last_payment_time', $user_id);
            $s2member_auto_eot_time            = get_user_option('s2member_auto_eot_time', $user_id);
            $s2member_file_download_access_log = get_user_option('s2member_file_download_access_log', $user_id);

            // I could also log this transaction, by creating a log entry in a static text file on-site.
            file_put_contents(WP_CONTENT_DIR.'/plugins/s2member-logs/my.log', 'Signup Notification Received for User ID: '.$user_id."\n", FILE_APPEND);
        }
        exit; // We can exit here. There's no reason to continue loading WordPress in this case.
    }
}

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