public static function save_users_key_request()
 {
     $emailRaw = trim($_POST['txt-key-request-email']);
     $email = filter_var($emailRaw, FILTER_SANITIZE_EMAIL);
     if (empty($email)) {
         $strResponse = '<div class="bg-warning message-box">Alamat e-mail kosong. Kami memerlukan alamat e-mail Anda untuk memvalidasi data. <a href="' . GameDev::$baseUrl . '/formulir">Kembali</a></div>';
     } else {
         if (!filter_var($email, FILTER_VALIDATE_EMAIL) === false) {
             // check if e-mail is already registered
             $queryCheck = 'select count(id) as num from gamedev__keys where email=:email';
             $statCheck = GameDev::$pdo->prepare($queryCheck);
             $statCheck->bindParam(':email', $email);
             $statCheck->execute();
             $resultCheck = $statCheck->fetch(PDO::FETCH_ASSOC);
             if ($resultCheck['num'] === 0) {
                 // e-mail is clear, save now
                 $dtNow = date('Y-m-d H:i:s');
                 $uniqueKey = md5($email . time());
                 $isActive = 1;
                 $querySave = 'insert into gamedev__keys (email, form_key, dt_request, is_active) values (:email, :form_key, :dt_request, :is_active)';
                 $statSave = GameDev::$pdo->prepare($querySave);
                 $statSave->bindParam(':email', $email);
                 $statSave->bindParam(':form_key', $uniqueKey);
                 $statSave->bindParam(':dt_request', $dtNow);
                 $statSave->bindParam(':is_active', $isActive);
                 $statSave->execute();
                 $strResponse = '<div class="bg-success message-box">Alamat e-mail Anda telah terdaftar. <a href="' . GameDev::$baseUrl . '/formulir/' . $uniqueKey . '">Lanjutkan ke formulir</a>.</div>';
             } else {
                 $strResponse = '<div class="bg-warning message-box">Alamat e-mail Anda, ' . $email . ', sudah didaftarkan. Kami tak bisa melanjutkan pemrosesan permintaan Anda. <a href="' . GameDev::$baseUrl . '/formulir">Kembali</a>.</div>';
             }
         } else {
             $strResponse = '<div class="bg-warning message-box">Alamat e-mail Anda, ' . $email . ', tak valid. <a href="' . GameDev::$baseUrl . '/formulir">Mohon cek kembali</a>. Kami memerlukan alamat e-mail Anda untuk memvalidasi data.</div>';
         }
     }
     $str = GameDev::get_page_header('html');
     $str .= GameDev::get_page_nav('formulir');
     $str .= '<div class="container">';
     $str .= '<div class="row">';
     $str .= '<div class="col-md-6 col-md-offset-3">';
     $str .= $strResponse;
     $str .= '</div>';
     // .col-md-6.col-md-offset-3
     $str .= '</div>';
     // .row
     $str .= '</div>';
     // .container
     $str .= GameDev::get_page_footer('html');
     echo $str;
     unset($str);
 }