WP_User $profile_user )
Fires after the ‘About Yourself’ settings table on the ‘Profile’ editing screen.
The action only fires if the current user is editing their own profile.
This action hook is typically used to output new fields or data to the bottom of WordPress’s user profile pages.
This hook only triggers when a user is viewing their own profile page. If you want to apply your hook to ALL profile pages (not just the current user) then you also need to use the edit_user_profile hook.
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do_action( 'show_user_profile', $profile_user );
See the edit_user_profile action for an example on how to add a form to the backend user edit screen and save some additional user meta data.
Example migrated from Codex: