Parent Terms in body_class

t5-parent-terms-body-class.php

<?php # -*- coding: utf-8 -*-
/**
 * Plugin Name: T5 Parent Terms in body_class
 * Description: Adds all parent terms of a term archive to <code>body_class()</code>.
 * Version:     2012.0.14
 * Author:      Fuxia Scholz
 * License:     MIT
 * License URI: http://www.opensource.org/licenses/mit-license.php
 */

add_filter( 'body_class', 't5_parent_terms_to_body_class' );

function t5_parent_terms_to_body_class( $classes )
{
	if ( ! isset ( get_queried_object()->taxonomy ) && ! is_singular() )
	{
		return $classes; // not a term archive and not a single page
	}

	$current_terms = array ();
	$new_classes   = array ();

	if ( is_singular() )
	{
		$post_id    = get_the_ID();
		$post       = get_post( $post_id );
		$taxonomies = get_object_taxonomies( $post );
		$terms      = array ();

		if ( empty ( $taxonomies ) )
		{
			return $classes;
		}

		foreach ( $taxonomies as $taxonomy )
		{
			$tax_terms = get_the_terms( $post_id, $taxonomy );
			! empty ( $tax_terms) and $terms = array_merge( $terms, $tax_terms );
		}

		foreach ( $terms as $term )
		{
			if ( 0 !== $term->parent )
			{
				$term_ancestors = get_ancestors(
					$term->term_id,
					$term->taxonomy
				);

				foreach ( $term_ancestors as $term_ancestor )
				{
					$term_data      = get_term( $term_ancestor, $term->taxonomy );
					$new_classes[] = esc_attr( "parent-$term->taxonomy-$term_data->slug" );
				}
			}
		}
	}
	else
	{
		// get all ancestors as an array.
		$ancestors = get_ancestors(
			get_queried_object_id(),
			get_queried_object()->taxonomy
		);

		if ( empty ( $ancestors ) )
		{
			return $classes;
		}

		foreach ( $ancestors as $ancestor )
		{
			$term          = get_term( $ancestor, get_queried_object()->taxonomy );
			$new_classes[] = esc_attr( "parent-$term->taxonomy-$term->slug" );
		}
	}

	// combine both
	$classes_out = array_merge( $classes, $new_classes );

	return array_unique( $classes_out );
}