Wordpress nav menu object

usage.php

function get_menu_tree($args) {
  $walker = new Walker_Nav_Menu_Object();

  wp_nav_menu(array_merge($args, array(
    'walker'  =>  $walker,
    'echo'    =>  FALSE
  )));

  return $walker->getOutput();
}

var_dump(get_menu_tree(array('menu' => 'header')));

Walker_Nav_Menu_Object.php

<?php

  class Walker_Nav_Menu_Object extends Walker_Nav_Menu
  {
    protected $scopes = array();

    public function __construct() {
      $this->scopes[] = (object)array(
        'children'  =>  array(),
        'parent'    =>  NULL
      );
    }

    public function getOutput() {
      return sizeof($this->scopes) ? $this->scopes[0] : array();
    }


    // Output scope

    public function &getScope() {
      return $this->scopes[sizeof($this->scopes) - 1];
    }

    public function unscopeEl() {
      array_pop($this->scopes);
    }
    public function scopeEl($el) {
      $this->scopes[] = $el;
    }


    // Walker pattern

    public function start_el(&$output, $item, $depth = 0, $args = array(), $id = 0) {
      $args  = apply_filters('nav_menu_item_args', $args, $item, $depth );
      $scope = &$this->getScope();
      $child = (object)array(
        'id'        =>  $id,
        'item'      =>  $item,
        'children'  =>  array(),
        'parent'    =>  &$scope,
        'attr'      =>  $this->getElAttributes($item, $depth, $args),
        'title'     =>  $this->getElTitle($item, $depth, $args)
      );

      // add child to scoped el
      $scope->children[] = $child;
      // set child as new scope
      $this->scopeEl($child);
    }

    public function end_el(&$output, $depth = 0, $args = array()) {
      // unscope ended child
      $this->unscopeEl();
    }

    public function start_lvl(&$output, $item, $depth = 0, $args = array()) {
      // nothing to do here
    }

    public function end_lvl(&$output, $depth = 0, $args = array()) {
      // nothing to do here
    }


    // Element HTML attributes

    public function getElTitle($item, $depth, $args) {
      $title = apply_filters('the_title', $item->title, $item->ID);
      $title = apply_filters('nav_menu_item_title', $title, $item, $args, $depth);
      return $title;
    }

    public function getElAttributes($item, $depth, $args) {
      $attr = array(
        'id'      =>  $this->getElIdAttribute($item, $depth, $args),
        'class'   =>  $this->getElClassAttribute($item, $depth, $args),
        'title'   =>  $this->getElAttribute($item, 'attr_title'),
        'target'  =>  $this->getElAttribute($item, 'target'),
        'rel'     =>  $this->getElAttribute($item, 'xfn'),
        'href'    =>  $this->getElAttribute($item, 'url')
      );

      $attr = apply_filters('nav_menu_link_attributes', $attr, $item, $args, $depth);
      return (object)$attr;
    }

    public function getElAttribute($item, $name) {
      return !empty($item->$name) ? $item->$name : '';
    }

    public function getElIdAttribute($item, $depth, $args) {
      return esc_attr(apply_filters( 'nav_menu_item_id', 'menu-item-'. $item->ID, $item, $args, $depth));
    }

    public function getElClassAttribute($item, $depth, $args) {
      $class    = empty($item->classes) ? array() : (array) $item->classes;
      $class[]  = 'menu-item-' . $item->ID;
      return apply_filters( 'nav_menu_css_class', array_filter($class), $item, $args, $depth);
    }
  }

?>