$whmusername = "cpanel_username";
$whmpassword = "cpanel_password";
$subdomain = 'newsubdomain';
$cpanel_ip = 'IP_ADDRESS'; //ip of cpanel or your_domain.com
$domain = "your_domain.com";
$query = "https://".$cpanel_ip."2083/json-api/cpanel?cpanel_jsonapi_module=SubDomain&cpanel_jsonapi_func=addsubdomain&cpanel_jsonapi_apiversion=2&dir=/public_html/".$subdomain.".".$domain."/&rootdomain=".$domain."&domain=".$subdomain."";
$curl = curl_init();
curl_setopt($curl, CURLOPT_SSL_VERIFYPEER,0);
curl_setopt($curl, CURLOPT_SSL_VERIFYHOST,0);
curl_setopt($curl, CURLOPT_HEADER,0);
curl_setopt($curl, CURLOPT_RETURNTRANSFER,1);
$header[0] = "Authorization: Basic " . base64_encode($whmusername.":".$whmpassword) . "
";
curl_setopt($curl, CURLOPT_HTTPHEADER, $header);
curl_setopt($curl, CURLOPT_URL, $query);
$result = curl_exec($curl);
curl_close($curl);