register_taxonomy() WP 1.0

Creates or modifies a taxonomy object.

Note: Do not use before the init hook.

A simple function for creating or modifying a taxonomy object based on the parameters given. If modifying an existing taxonomy object, note that the $object_type value from the original registration will be overwritten.

Return

WP_Taxonomy|WP_Error. The registered taxonomy object on success, WP_Error object on failure.

Usage

register_taxonomy( $taxonomy, $object_type, $args );

$taxonomy(string) (required)

Taxonomy key, must not exceed 32 characters.

$object_type(array|string) (required)

Object type or array of object types with which the taxonomy should be associated.

$args(array|string)

Array or query string of arguments for registering a taxonomy.

• labels(string[])
  An array of labels for this taxonomy. By default, Tag labels are used for non-hierarchical taxonomies, and Category labels are used for hierarchical taxonomies. See accepted values in get_taxonomy_labels().
  Default: empty array

• description(string)
  A short descriptive summary of what the taxonomy is for.
  Default: ''

• public(true|false)
  Whether a taxonomy is intended for use publicly either via the admin interface or by front-end users. The default settings of $publicly_queryable, $show_ui, and $show_in_nav_menus are inherited from $public.

• publicly_queryable(true|false)
  Whether the taxonomy is publicly queryable. If not set, the default is inherited from $public

• hierarchical(true|false)
  Whether the taxonomy is hierarchical.
  Default: false

• show_ui(true|false)
  Whether to generate and allow a UI for managing terms in this taxonomy in the admin. If not set, the default is inherited from $public (default true).

• show_in_menu(true|false)
  Whether to show the taxonomy in the admin menu. If true, the taxonomy is shown as a submenu of the object type menu. If false, no menu is shown. $show_ui must be true. If not set.
  Default: inherited from $show_ui (default true)

• show_in_nav_menus(true|false)
  Makes this taxonomy available for selection in navigation menus. If not set, the default is inherited from $public (default true).

• show_in_rest(true|false)
  Whether to include the taxonomy in the REST API. Set this to true for the taxonomy to be available in the block editor.

• rest_base(string)
  To change the base url of REST API route.
  Default: $taxonomy

• rest_controller_class(string)
  REST API Controller class name.
  Default: 'WP_REST_Terms_Controller'

• show_tagcloud(true|false)
  Whether to list the taxonomy in the Tag Cloud Widget controls. If not set, the default is inherited from $show_ui (default true).

• show_in_quick_edit(true|false)
  Whether to show the taxonomy in the quick/bulk edit panel. It not set, the default is inherited from $show_ui (default true).

• show_admin_column(true|false)
  Whether to display a column for the taxonomy on its post type listing screens.
  Default: false

• meta_box_cb(true|false|callable)
  Provide a callback function for the meta box display. If not set, post_categories_meta_box() is used for hierarchical taxonomies, and post_tags_meta_box() is used for non-hierarchical. If false, no meta box is shown.

• meta_box_sanitize_cb(callable)
  Callback function for sanitizing taxonomy data saved from a meta box. If no callback is defined, an appropriate one is determined based on the value of $meta_box_cb.

• capabilities(string[])
  Array of capabilities for this taxonomy.

  • manage_terms(string)
    Default 'manage_categories'.

  • edit_terms(string)
    Default 'manage_categories'.

  • delete_terms(string)
    Default 'manage_categories'.

  • assign_terms(string)
    Default 'edit_posts'.

• rewrite(true|false|array)
  Triggers the handling of rewrites for this taxonomy. To prevent rewrite, set to false. To specify rewrite rules, an array can be passed with any of these keys:
  Default: true, using $taxonomy as slug

  • slug(string)
    Customize the permastruct slug.
    Default: $taxonomy key

  • with_front(true|false)
    Should the permastruct be prepended with WP_Rewrite::$front.
    Default: true

  • hierarchical(true|false)
    Either hierarchical rewrite tag or not.
    Default: false

  • ep_mask(int)
    Assign an endpoint mask.
    Default: EP_NONE

• query_var(string|true|false)
  Sets the query var key for this taxonomy. If false, a taxonomy cannot be loaded at ?{query_var}={term_slug}. If a string, the query ?{query_var}={term_slug} will be valid.
  Default: $taxonomy key

• update_count_callback(callable)
  Works much like a hook, in that it will be called when the count is updated. Default _update_generic_term_count() for taxonomies attached to other object types, such as users.
  Default: _update_post_term_count() for taxonomies attached to post types, which confirms that the objects are published before counting them

• default_term(string|array)
  Default term to be used for the taxonomy.

  • name(string)
    Name of default term.

  • slug(string)
    Slug for default term.
    Default: ''

  • description(string)
    Description for default term.
    Default: ''

• sort(true|false)
  Whether terms in this taxonomy should be sorted in the order they are provided to wp_set_object_terms().
  Default: null which equates to false

• args(array)
  Array of arguments to automatically use inside wp_get_object_terms() for this taxonomy.

• _builtin(true|false)
  This taxonomy is a "built-in" taxonomy. INTERNAL USE ONLY! Default false.

Notes

• Global. Array. $wp_taxonomies Registered taxonomies.

Changelog

Code of register_taxonomy() register taxonomy ^{WP 5.7.2}

<?php
function register_taxonomy( $taxonomy, $object_type, $args = array() ) {
	global $wp_taxonomies;

	if ( ! is_array( $wp_taxonomies ) ) {
		$wp_taxonomies = array();
	}

	$args = wp_parse_args( $args );

	if ( empty( $taxonomy ) || strlen( $taxonomy ) > 32 ) {
		_doing_it_wrong( __FUNCTION__, __( 'Taxonomy names must be between 1 and 32 characters in length.' ), '4.2.0' );
		return new WP_Error( 'taxonomy_length_invalid', __( 'Taxonomy names must be between 1 and 32 characters in length.' ) );
	}

	$taxonomy_object = new WP_Taxonomy( $taxonomy, $object_type, $args );
	$taxonomy_object->add_rewrite_rules();

	$wp_taxonomies[ $taxonomy ] = $taxonomy_object;

	$taxonomy_object->add_hooks();

	// Add default term.
	if ( ! empty( $taxonomy_object->default_term ) ) {
		$term = term_exists( $taxonomy_object->default_term['name'], $taxonomy );
		if ( $term ) {
			update_option( 'default_term_' . $taxonomy_object->name, $term['term_id'] );
		} else {
			$term = wp_insert_term(
				$taxonomy_object->default_term['name'],
				$taxonomy,
				array(
					'slug'        => sanitize_title( $taxonomy_object->default_term['slug'] ),
					'description' => $taxonomy_object->default_term['description'],
				)
			);

			// Update `term_id` in options.
			if ( ! is_wp_error( $term ) ) {
				update_option( 'default_term_' . $taxonomy_object->name, $term['term_id'] );
			}
		}
	}

	/**
	 * Fires after a taxonomy is registered.
	 *
	 * @since 3.3.0
	 *
	 * @param string       $taxonomy    Taxonomy slug.
	 * @param array|string $object_type Object type or array of object types.
	 * @param array        $args        Array of taxonomy registration arguments.
	 */
	do_action( 'registered_taxonomy', $taxonomy, $object_type, (array) $taxonomy_object );

	return $taxonomy_object;
}

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