WordPressの記事検索にカテゴリ名・タグ名も含める方法

//-----------------------------------------------------
// 検索対象にカテゴリを含める
//-----------------------------------------------------
function custom_search($search, $wp_query) {
	global $wpdb;

	//検索ページ以外
	if (!$wp_query->is_search)
	return $search;

	if (!isset($wp_query->query_vars))
	return $search;

	$search_words = explode(' ', isset($wp_query->query_vars['s']) ? $wp_query->query_vars['s'] : '');
	if ( count($search_words) > 0 ) {
		$search = '';
		foreach ( $search_words as $word ) {
			if ( !empty($word) ) {
				$search_word = $wpdb-> _escape("%{$word}%");
				$search .= " AND (
						{$wpdb->posts}.post_title LIKE '{$search_word}'
						OR {$wpdb->posts}.post_content LIKE '{$search_word}'
            /*タグ名・カテゴリ名を検索対象に含める記述 start*/
						OR {$wpdb->posts}.ID IN (
							SELECT distinct r.object_id
							FROM {$wpdb->term_relationships} AS r
							INNER JOIN {$wpdb->term_taxonomy} AS tt ON r.term_taxonomy_id = tt.term_taxonomy_id
							INNER JOIN {$wpdb->terms} AS t ON tt.term_id = t.term_id
							WHERE t.name LIKE '{$search_word}'
						OR t.slug LIKE '{$search_word}'
						OR tt.description LIKE '{$search_word}'
						)
          /*タグ名・カテゴリ名を検索対象に含める記述 end*/
				) ";
			}
		}
	}

	return $search;
}
add_filter('posts_search','custom_search', 10, 2);