$type = $data['type'];
$start = date("Y-m-d");
$end = date("Y-m-d", strtotime("+1 month")); // یا بر اساس نوع اشتراک

switch ($type) {
    case "monthly":
        $end = date("Y-m-d", strtotime("+1 month"));
        break;
    case "quarterly":
        $end = date("Y-m-d", strtotime("+3 months"));
        break;
    case "vip":
        $end = date("Y-m-d", strtotime("+1 year"));
        break;
}

$stmt = $conn->prepare("INSERT INTO subscriptions (user_id, type, start_date, end_date, status) VALUES (?, ?, ?, ?, 'active')");
$stmt->bind_param("isss", $user_id, $type, $start, $end);
$stmt->execute();