보이지 않는 CAPTCHA — PHP

# No package, no dependency.
# PHP 8.1 or newer with the cURL extension — that is all.
php -m | grep curl

<!-- In <head> or before </body> of every page with a form -->
<script src="https://api.silentshield.io/client.js?k=YOUR_API_KEY" defer></script>

<?php
$api_key = "YOUR_API_KEY";
$nonce = $_POST['behavior_nonce'] ?? ''; // hidden input injected by client.js

$payload = json_encode(['nonce' => $nonce]);

$ch = curl_init("https://api.silentshield.io/api/v1/captcha/verify-nonce");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, [
  "Content-Type: application/json",
  "X-Api-Key: " . $api_key,
]);
curl_setopt($ch, CURLOPT_POSTFIELDS, $payload);
curl_setopt($ch, CURLOPT_TIMEOUT, 5);

$response = curl_exec($ch);
$http_code = curl_getinfo($ch, CURLINFO_HTTP_CODE);

if ($http_code !== 200) {
  error_log("SilentShield API error: " . $http_code);
  // Fail secure: reject on API errors
  exit(json_encode(['error' => 'Verification failed']));
}

$data = json_decode($response, true);
$is_human = $data['ok'] && $data['verdict'] === 'human' && $data['confidence'] >= 0.7;

if (!$is_human) {
  error_log("Bot detected. Nonce: " . ($data['requested_nonce'] ?? 'unknown'));
  exit(json_encode(['error' => 'Bot detected']));
}