ukaiautomation/api/license/webuy/index.php

<?php
header('Content-Type: text/plain');

// Simple validation - customize to your needs
// Options: hardcoded, database lookup, check against allowed machine IDs, etc.

$valid = false; // Replace with your validation logic

if ($valid) {
    echo 'valid';
} else {
    echo 'unpaid invoice';
}