_access_denied_splash() – Displays an access denied message when a user tries to view a site’s dashboard they do not have access to.
_admin_notice_post_locked() – Outputs the HTML for the notice to say that someone else is editing or has taken over editing of this post.
_delete_attachment_theme_mod() – Checks an attachment being deleted to see if it’s a header or background image.
_filter_query_attachment_filenames() – Filter the SQL clauses of an attachment query to include filenames.
_get_additional_user_keys() – Returns a list of meta keys to be (maybe) populated in wp_update_user().
_remove_qs_args_if_not_in_url() – Removes arguments from a query string if they are not present in a URL DO NOT use this in plugin code.
_rest_array_intersect_key_recursive() – Recursively computes the intersection of arrays using keys for comparison.
_wp_add_global_attributes() – Helper function to add global attributes to a tag in the allowed html list.
_wp_admin_bar_init() – Instantiate the admin bar object and set it up as a global for access elsewhere.
_wp_ajax_delete_comment_response() – Sends back current comment total and new page links if they need to be updated.
_wp_auto_add_pages_to_menu() – Automatically add newly published page objects to menus with that as an option.
_wp_keep_alive_customize_changeset_dependent_auto_drafts() – Make sure that auto-draft posts get their post_date bumped or status changed to draft to prevent premature garbage-collection.
add_existing_user_to_blog() – Add a user to a blog based on details from maybe_add_existing_user_to_blog().