Issuing LetsEncrypt SSL Certificates using XMLAPI for cPanel

Question

I'm currently working with XMLAPI in PHP with cPanel to automatically create subdomains for my customers. I've managed to create the script that allows for subdomain creation but I'm having a hard time wrapping my head around using XMLAPI to issue certificates using the LetsEncrypt certificate issuer inside cPanel. Here is the script I use to create subdomains:

$subdomain = $usrdomain;
$cpanelusr = 'myusername';
$cpanelpass = decryptIt(decryptKey("Jzc5WZO5LfOYonIVSNfgQKmQM0qCiUl7Z3ALKqLI41kpwQQdcGn9kQhjH1k04LImjAgRK8B4Q54DPTyfKLtYXA=="));
$xmlapi = new xmlapi('server ip');
$xmlapi->set_port( 2083 );
$xmlapi->password_auth($cpanelusr,$cpanelpass);
$xmlapi->set_debug(0);
$result = $xmlapi->api1_query($cpanelusr, 'SubDomain', 'addsubdomain', array($subdomain,'mydomain.com',0,0, '/public_html/' . $subdomain . '/'));

and here is what I'm trying to use to issue certificates:

$xmlapi = new xmlapi('server ip');
$xmlapi->set_port( 2083 );
$xmlapi->password_auth($cpanelusr,$cpanelpass);
$xmlapi->set_debug(0);
$result = $xmlapi->api1_query($cpanelusr, 'letsencrypt', 'issue', array($subdomain,'mydomain.com',0,0, ''));