wp_list_categories – print a tree

Does it seem it cannot be done in a single call? Not that because is a single call it will be faster tho.

Let’s say I want to print category “Books” and its childs. I only came to this solution:

$books_cat_id = 7;
$childs = get_categories( array( 'child_of' => $books_cat_id ) );
$ids = array( $books_cat_id );
foreach( $childs as $child ) {
	$ids[] = $child->term_id;
}
$html = wp_list_categories( array(
	'title_li' => '',
	'hide_empty' => 0,
	'echo' => 1,
	'show_option_none' => '',
	'include' => implode( ',', $ids )
) );

That’s some pretty nasty stuff.