Create a subdomain on DigitalOcean without using Composer

create_subdomain.php

<?php

$data = array(
    "type" => "A",
    "name" => "SUBDOMAIN",
    "data" => "188.*****", // your ip address
    "ttl" => 1800
);

$ch = curl_init();

curl_setopt($ch, CURLOPT_URL, "https://api.digitalocean.com/v2/domains/YOURDOMAIN.COM/records");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($data));

$headers = array(
    "Content-Type: application/json",
    "Authorization: Bearer dop_v1_3b374f34******" // your api key
);

curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);

$result = curl_exec($ch);

curl_close($ch);

$result = json_decode($result, true);
print_r($result);