// --- OPTION B: store in MySQL via PDO ---

$dbHost = 'localhost';
$dbName = 'your_cpanel_dbname';
$dbUser = 'your_cpanel_dbuser';
$dbPass = 'your_cpanel_dbpass';

try {
    $dsn = "mysql:host=$dbHost;dbname=$dbName;charset=utf8mb4";
    $pdo = new PDO($dsn, $dbUser, $dbPass, [
        PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
    ]);

    $stmt = $pdo->prepare("
        INSERT INTO racklet_readings (
          serial, fw_version, ip, ip_mode, dht_temp, dht_hum,
          chip_temp, uptime_ms, free_heap, sd_card,
          wifi_ssid, wifi_rssi, wifi_channel, remote_ip
        ) VALUES (
          :serial, :fw_version, :ip, :ip_mode, :dht_temp, :dht_hum,
          :chip_temp, :uptime_ms, :free_heap, :sd_card,
          :wifi_ssid, :wifi_rssi, :wifi_channel, :remote_ip
        )
    ");

    $stmt->execute([
        ':serial'      => $serial,
        ':fw_version'  => $fwVersion,
        ':ip'          => $ip,
        ':ip_mode'     => $ipMode,
        ':dht_temp'    => $dhtTemp,
        ':dht_hum'     => $dhtHum,
        ':chip_temp'   => $chipTemp,
        ':uptime_ms'   => $uptimeMs,
        ':free_heap'   => $freeHeap,
        ':sd_card'     => is_null($sdCard) ? null : (int)!!$sdCard,
        ':wifi_ssid'   => $wifiSsid,
        ':wifi_rssi'   => $wifiRssi,
        ':wifi_channel'=> $wifiChannel,
        ':remote_ip'   => $_SERVER['REMOTE_ADDR'] ?? null,
    ]);

    header('Content-Type: application/json');
    echo json_encode([
        'status'   => 'ok',
        'message'  => 'Data stored in DB',
        'id'       => $pdo->lastInsertId(),
    ]);
} catch (PDOException $e) {
    http_response_code(500);
    header('Content-Type: application/json');
    echo json_encode([
        'status'  => 'error',
        'message' => 'DB error',
        'error'   => $e->getMessage(),
    ]);
}