wp_list_categories( array|string $args = '' )

显示或检索类别的HTML列表。
Display or retrieve the HTML list of categories.

源码（Source）

/**
 * Display or retrieve the HTML list of categories.
 *
 * The list of arguments is below:
 *     'show_option_all' (string) - Text to display for showing all categories.
 *     'orderby' (string) default is 'ID' - What column to use for ordering the
 * categories.
 *     'order' (string) default is 'ASC' - What direction to order categories.
 *     'show_count' (bool|int) default is 0 - Whether to show how many posts are
 * in the category.
 *     'hide_empty' (bool|int) default is 1 - Whether to hide categories that
 * don't have any posts attached to them.
 *     'use_desc_for_title' (bool|int) default is 1 - Whether to use the
 * category description as the title attribute.
 *     'feed' - See {@link get_categories()}.
 *     'feed_type' - See {@link get_categories()}.
 *     'feed_image' - See {@link get_categories()}.
 *     'child_of' (int) default is 0 - See {@link get_categories()}.
 *     'exclude' (string) - See {@link get_categories()}.
 *     'exclude_tree' (string) - See {@link get_categories()}.
 *     'echo' (bool|int) default is 1 - Whether to display or retrieve content.
 *     'current_category' (int) - See {@link get_categories()}.
 *     'hierarchical' (bool) - See {@link get_categories()}.
 *     'title_li' (string) - See {@link get_categories()}.
 *     'depth' (int) - The max depth.
 *
 * @since 2.1.0
 *
 * @param string|array $args Optional. Override default arguments.
 * @return false|string HTML content only if 'echo' argument is 0.
 */
function wp_list_categories( $args = '' ) {
	$defaults = array(
		'show_option_all' => '', 'show_option_none' => __('No categories'),
		'orderby' => 'name', 'order' => 'ASC',
		'style' => 'list',
		'show_count' => 0, 'hide_empty' => 1,
		'use_desc_for_title' => 1, 'child_of' => 0,
		'feed' => '', 'feed_type' => '',
		'feed_image' => '', 'exclude' => '',
		'exclude_tree' => '', 'current_category' => 0,
		'hierarchical' => true, 'title_li' => __( 'Categories' ),
		'echo' => 1, 'depth' => 0,
		'taxonomy' => 'category'
	);

	$r = wp_parse_args( $args, $defaults );

	if ( !isset( $r['pad_counts'] ) && $r['show_count'] && $r['hierarchical'] )
		$r['pad_counts'] = true;

	if ( true == $r['hierarchical'] ) {
		$r['exclude_tree'] = $r['exclude'];
		$r['exclude'] = '';
	}

	if ( ! isset( $r['class'] ) )
		$r['class'] = ( 'category' == $r['taxonomy'] ) ? 'categories' : $r['taxonomy'];

	if ( ! taxonomy_exists( $r['taxonomy'] ) ) {
		return false;
	}

	$show_option_all = $r['show_option_all'];
	$show_option_none = $r['show_option_none'];

	$categories = get_categories( $r );

	$output = '';
	if ( $r['title_li'] && 'list' == $r['style'] ) {
		$output = '' . $r['title_li'] . '';
	}
	if ( empty( $categories ) ) {
		if ( ! empty( $show_option_none ) ) {
			if ( 'list' == $r['style'] ) {
				$output .= '' . $show_option_none . '';
			} else {
				$output .= $show_option_none;
			}
		}
	} else {
		if ( ! empty( $show_option_all ) ) {

			$posts_page = '';

			// For taxonomies that belong only to custom post types, point to a valid archive.
			$taxonomy_object = get_taxonomy( $r['taxonomy'] );
			if ( ! in_array( 'post', $taxonomy_object->object_type ) && ! in_array( 'page', $taxonomy_object->object_type ) ) {
				foreach ( $taxonomy_object->object_type as $object_type ) {
					$_object_type = get_post_type_object( $object_type );

					// Grab the first one.
					if ( ! empty( $_object_type->has_archive ) ) {
						$posts_page = get_post_type_archive_link( $object_type );
						break;
					}
				}
			}

			// Fallback for the 'All' link is the front page.
			if ( ! $posts_page ) {
				$posts_page = 'page' == get_option( 'show_on_front' ) && get_option( 'page_for_posts' ) ? get_permalink( get_option( 'page_for_posts' ) ) : home_url( '/' );
			}

			$posts_page = esc_url( $posts_page );
			if ( 'list' == $r['style'] ) {
				$output .= "$show_option_all";
			} else {
				$output .= "$show_option_all";
			}
		}

		if ( empty( $r['current_category'] ) && ( is_category() || is_tax() || is_tag() ) ) {
			$current_term_object = get_queried_object();
			if ( $current_term_object && $r['taxonomy'] === $current_term_object->taxonomy ) {
				$r['current_category'] = get_queried_object_id();
			}
		}

		if ( $r['hierarchical'] ) {
			$depth = $r['depth'];
		} else {
			$depth = -1; // Flat.
		}
		$output .= walk_category_tree( $categories, $depth, $r );
	}

	if ( $r['title_li'] && 'list' == $r['style'] )
		$output .= '';

	/**
	 * Filter the HTML output of a taxonomy list.
	 *
	 * @since 2.1.0
	 *
	 * @param string $output HTML output.
	 * @param array  $args   An array of taxonomy-listing arguments.
	 */
	$html = apply_filters( 'wp_list_categories', $output, $args );

	if ( $r['echo'] ) {
		echo $html;
	} else {
		return $html;
	}
}

笔记（Notes）