# Upgrading from 3.1.5 to 3.1.6

Before performing an update you should take your site offline by replacing the index.php file with a static one.

## Step 1: Update your CodeIgniter files

Replace all files and directories in your system/ directory.

Note

If you have any custom developed files in these directories, please make copies of them first.

## Step 2: Remove usage of the APC Cache driver (deprecation)

The Cache Library 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.

Note

The driver is still available, but you’re strongly encouraged to remove its usage sooner rather than later.