Returning a non-null value will effectively short-circuit the function, returning that value instead.
(bool|null) The value to return, if not null.
(int) The site ID that is being checked.
In WordPress theme and development, Hooks are functions that can be applied to an Action or a Filter in WordPress. Actions and Filters in WordPress are functions that can be altered by theme and plugin developers to change the default WordPress functionality.
Functions used to alter Actions/Filters in WordPress can be hooked into WordPress. In any case, note that actions and filters are not some thing very similar. Actions are functions performed when a specific occasion happens in WordPress. Filters enable you to change certain functions. Arguments used to hook the two filters and actions appear to be identical. Be that as it may, they are different in functionality and how they carry on.