Create a new subdomain and MySQL database via WHM or cPanel API with PHP

I had hoped this was an easy task to perform, but now that I've researched it in depth for a couple of days, the whole process seems much more complicated than I had originally thought.

I would like to create a new subdomain under mydomain.com, e.g. test123.mydomain.com, using PHP via either the WHM API 1 or cPanel API 2 and subsequently a new MySQL database to be used under that new subdomain.

I'm assuming I need to authenticate with WHM first (using a WHM remote API token?), then make the call to the appropriate API module and function, and finally check the response for success or errors. Since I'm doing this with PHP, I'm assuming I would need to do this all via curl. In the cPanel API 2 docs, I see this call:

https://hostname.example.com:2087/cpsess##########/json-api/cpanel?cpanel_jsonapi_user=user&cpanel_jsonapi_apiversion=2&cpanel_jsonapi_module=SubDomain&cpanel_jsonapi_func=addsubdomain&domain=subdomain&rootdomain=example.com&dir=%2Fpublic_html%2Fdirectory_name&disallowdot=1

Unfortunately, that's not much help since I don't have an open "cpsess" as I'm doing this via a PHP script and replacing the "cpsess##########" with an WHM remote API token doesn't work either. I've tried a handful of different methods and so far the only one I can get to work is the cPanel API 1 example for listing accounts on the server...it works perfectly, but it's on API 1 which doesn't have the module available to create subdomains:

function getUserAccountList($user,$token){
    $userList = "";
    $query = "https://hostname.example.com:2087/json-api/listaccts?api.version=1";
    $curl = curl_init();
    curl_setopt($curl, CURLOPT_SSL_VERIFYHOST,0);
    curl_setopt($curl, CURLOPT_SSL_VERIFYPEER,0);
    curl_setopt($curl, CURLOPT_RETURNTRANSFER,1);
    $header[0] = "Authorization: whm $user:$token";
    curl_setopt($curl,CURLOPT_HTTPHEADER,$header);
    curl_setopt($curl, CURLOPT_URL, $query);
    $result = curl_exec($curl);
    $http_status = curl_getinfo($curl, CURLINFO_HTTP_CODE);
    if ($http_status != 200) {
        $userList = "[!] Error: " . $http_status . " returned\n";
    } else {
        $json = json_decode($result);
        $userList.= "[+] Current cPanel users on the system:<BR><BR>";
        foreach ($json->{'data'}->{'acct'} as $userdetails) {
            $userList.= $userdetails->{'user'} . "<BR>";
        }
    }
    curl_close($curl);
    return $userList;
}

The question is: how do I create a new subdomain and MySQL database with a PHP script using either the WHM API 1 or cPanel API 2? Any help would be greatly appreciated!