{$action} WordPress Action Hook
The {$action} Wordpress hook is a powerful tool that allows developers to extend the functionality of their Wordpress site. This hook is called whenever an action is performed on a Wordpress site, such as when a post is published or a user is registered. By using this hook, developers can add their own custom code to perform an action when these events occur. This makes it possible to create custom features or modify the behavior of existing features on a Wordpress site.
do_action_deprecated( "{$action}" ) #
If the ‘postcustom’ meta box is enabled, then we need to perform some extra initialization on it.