Function: If Multisite is enabled.

Function: Retrieve the current site ID.

Function: Set the database table prefix and the format specifiers for database table columns.

Function: Toggle `$_wp_using_ext_object_cache` on and off without directly touching global.

Function: Start the WordPress object cache.

Function: Redirect to the installer if WordPress is not installed.

Function: Retrieve an array of must-use plugin files.

Function: Retrieve an array of active and valid plugin files.

Function: Set internal encoding.

Function: Add magic quotes to `$_GET`, `$_POST`, `$_COOKIE`, and `$_SERVER`.