Function: Determines whether the current request is for a site’s administrative interface.

Function: Determines whether the current request is for the network administrative interface.

Function: Determines whether the current request is for a user admin screen.

Function: If Multisite is enabled.

Function: Retrieve the current site ID.

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.