function smarty_modifier_category_menu ($input) {
	// This function takes a nested array as input and produces
	// nested lists from it. It can handle arrays with one or many
	// root nodes
	
	$html = "<ul>\n";
	foreach ($input as $menu) {
		$html .= "<li><a href=\"{$menu['url']}\">{$menu['title']}</a>";
		if (!empty($menu['sub'])) {
			$html .= smarty_modifier_category_menu($menu['sub']);
		}
		$html .= "</li>\n";
	}
	$html .= "</ul>\n";
	return $html;
}