Cleans all user caches.

Gets the number of posts written by a list of users.

Gets the number of posts a user has written.

Counts number of users who have each of the user roles.

Removes metadata matching criteria from a user.

Deletes user option with global blog capability.

Determines whether the given email exists.

Gets the sites a user belongs to.

Gets the current user’s ID.

Creates, stores, then returns a password reset key for user.