Custom Walker: how to get ID in function start_lvl


class ThemeTruck_Nav_Walker extends Walker_Nav_Menu {
private $curItem;
// retrieve the curItem
function start_lvl(&$output, $depth = 0, $args = array()) {
var_dump($this->curItem );
}
// store the curItem
function start_el(&$output, $item, $depth = 0, $args = array(), $id = 0) {
$this->curItem = $item;
}
}