Запустите новую вкладку и обновите оригинальную страницу Codeigniter

<form action="newpage.php" method="post" target="_blank" onsubmit="javascript: setTimeout(function(){location.reload();}, 1000);return true;">
  Next Availiable ID: <input type="text" name="id" value="<?= $nextid ?>"><br/>
  Your Name: <input type="text" name="thename" maxlength="64"><br/>
  <button type="submit">Go!</button>
</form>
Uninterested Unicorn