Help with output of post classes using apply_filters

Solved it with generous help using join()…

function start_el(&$output, $page, $depth = 0, $args = array(), $id = 0) {
        if ( $depth )
            $indent = str_repeat("\t", $depth);
        else
            $indent="";

        extract($args, EXTR_SKIP);

        $output .= $indent . '<li id="item_'.$page->ID.'" class="'.join( " ", get_post_class( "", $page->ID )).'"><span>'.apply_filters( 'the_title', $page->post_title, $page->ID ).'</span>';
    }