_() – WordPress implementation for PHP functions either missing from older PHP versions or not included by default.
_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.
_block_template_render_title_tag() – Displays title tag with content, regardless of whether theme has title-tag support.
_block_template_render_without_post_block_context() – Removes post details from block context when rendering a block template.
_canonical_charset() – Retrieve a canonical form of the provided charset appropriate for passing to PHP functions such as htmlspecialchars() and charset html attributes.
_clear_modified_cache_on_transition_comment_status() – Clear the lastcommentmodified cached value when a comment status is changed.
_close_comments_for_old_post() – Close comments on an old post. Hooked to comments_open and pings_open.
_close_comments_for_old_posts() – Close comments on old posts on the fly, without any extra DB queries. Hooked to the_posts.
_copy_dir() – Copies a directory from one location to another via the WordPress Filesystem Abstraction.
_custom_header_background_just_in_time() – Registers the internal custom header and background routines.
_custom_logo_header_styles() – Adds CSS to hide header text for custom logo, based on Customizer setting.
_deep_replace() – Perform a deep string replace operation to ensure the values in $search are no longer present
_delete_attachment_theme_mod() – Checks an attachment being deleted to see if it’s a header or background image.
_delete_site_logo_on_remove_custom_logo_on_setup_theme() – Hooks `_delete_site_logo_on_remove_custom_logo` in `update_option_theme_mods_$theme`.
_delete_site_logo_on_remove_custom_logo() – Deletes the site_logo when the custom_logo theme mod is removed.
_delete_site_logo_on_remove_theme_mods() – Deletes the site logo when all theme mods are being removed.
_excerpt_render_inner_blocks() – Render inner blocks from the allowed wrapper blocks for generating an excerpt.
_excerpt_render_inner_columns_blocks() – Render inner blocks from the `core/columns` block for generating an excerpt.
_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().
_get_custom_object_labels() – Build an object with custom-something object (post type, taxonomy) labels out of a custom-something object
_get_path_to_translation_from_lang_dir() – Gets the path to a translation file in the languages directory for the current locale.
_get_path_to_translation() – Gets the path to a translation file for loading a textdomain just in time.
_get_plugin_data_markup_translate() – Sanitizes plugin data, optionally adds markup, optionally translates.
_http_build_query() – From php.net (modified by Mark Jaquith to behave like the native PHP5 function).
_jsonp_wp_die_handler() – Kills WordPress execution and displays JSONP response with an error message.
