在執行升級之前，你應該更換 index.php 為靜態檔案，將網站導向此靜態網頁。
取代 system/ 目錄打下的所有目錄與檔案
.. 提醒:: 假如您有修改此目錄底下的檔案，麻煩請先複製備份。
The :doc:`Cache Library <../libraries/caching>` APC driver is now deprecated, as the APC extension is effectively dead, as explained in its PHP Manual page.
If your application happens to be using it, you can switch to another cache driver, as APC support will be removed in a future CodeIgniter version.
.. 提醒:: The driver is still available, but you're strongly encouraged
to remove its usage sooner rather than later.