all-in-one/php/domain-validator.php

<?php
declare(strict_types=1);

$domain = '';
if (isset($_GET['domain']) && is_string($_GET['domain'])) {
    $domain = $_GET['domain'];
}

if (!str_contains($domain, '.')) { 
    http_response_code(400); 
} elseif (str_contains($domain, '/')) { 
    http_response_code(400);  
} elseif (str_contains($domain, ':')) { 
    http_response_code(400);  
} elseif (filter_var($domain, FILTER_VALIDATE_DOMAIN, FILTER_FLAG_HOSTNAME) === false) { 
    http_response_code(400); 
} elseif (filter_var($domain, FILTER_VALIDATE_IP)) { 
    http_response_code(400); 
} else {
    // Commented because logging is disabled as otherwise all attempts will be logged which spams the logs
    // error_log($domain . ' was accepted as valid domain.');
    http_response_code(200);
}