List only upper level Pages

<?php
/*
This code will (I hope) use wp_list_pages to list all but the last sublevel in a
hierarchy of pages.  It is in response to this WP Support topic:

http://wordpress.org/support/topic/dynamically-limit-depth-of-wp_list_pages
*/

$parent = 2192; // The ID of the parent Page

function array_max_depth($array, $depth = 0) {
   // The array here is and entry in the $refs array.
   // The max depth is the sum of:
   //    1 for the parent
   //    1 for each 'children' element
   //    1 for each child ID in 'children'
   // To get the true depth, subtract 1 for the parent, divide by 2 to get
   // the number of children, and add back the 1 for the parent.
   // true depth = ((max_depth - 1) / 2) + 1
   $max_sub_depth = 0;
   foreach (array_filter($array, 'is_array') as $subarray) {
      $max_sub_depth = max(
         $max_sub_depth,
         array_max_depth($subarray, $depth)
      );
    }
    return $max_sub_depth + $depth + 1;
}

function get_includes($keys,&$includes,&$parent_data) {
   // Recursively walk $parent_data accumulating included page ids
   foreach ($keys as $parentid) {
      // print_r('<p><pre>KEYS: ');print_r($keys);print_r('<br />');
      $this_data = $parent_data[$parentid];
      // print_r("THISDATA: $parentid ");print_r($this_data);print_r('<br />');

      if ($this_data['maxdepth'] > 1) {
         $includes = array_merge($includes,array_keys($this_data['children']));
         // print_r("<br />INCLUDES: ");print_r($includes);print_r('</pre></p>');

         get_includes(array_keys($this_data['children']), $includes, $parent_data);
      }
   }
}

$pages = get_pages(array('child_of' => $parent));
//print_r($pages);

if($pages) {
   $refs = array();

   foreach ($pages as $page) {
      // Create $refs as an array of page IDs with keys 'post_parent',
      // 'post_title', and 'children'.  The 'children' key contains an array of
      // IDs of children of this page.

      $data = array('ID' => $page->ID, 'post_parent' => $page->post_parent, 'post_title' => $page->post_title );
      $thisref = &$refs[ $data['ID'] ];

      $thisref['post_parent'] = $data['post_parent'];
      $thisref['post_title'] = $data['post_title'];

      $refs[ $data['post_parent'] ]['children'][ $data['ID'] ] = &$thisref;
   }
   //print_r('<p><pre>REFS: ');print_r($refs);print_r('</pre></p>');

   $new_parent = array('children' => array(), 'maxdepth' => 0);
   $parents[$parent] = $new_parent;
   foreach ($pages as $page) {
      if (false === array_search($page->post_parent,array_keys($parents),true)) $parents[$page->post_parent] = $new_parent;
      $indent = array_search($page->post_parent,array_keys($parents),true);
      $depth =  ((array_max_depth($refs[$page->ID]) - 1) / 2 ) + 1;
      $parents[$page->post_parent]['children'][$page->ID] = $depth;
      if ($depth > $parents[$page->post_parent]['maxdepth']) $parents[$page->post_parent]['maxdepth'] = $depth;
      // echo str_repeat('&nbsp;',$indent * 5);
      // echo "ID: $page->ID  PARENT:$page->post_parent DEPTH:$depth $TITLE:$page->post_title<br />";
   }
   // print_r('<p><pre>PARENTS: ');print_r($parents);print_r('</pre></p>');

   $includes = array_merge(array($parent),array_keys($parents[$parent]['children']));  // Always include the parent and its direct children
   // print_r('<p><pre>INCLUDES: ');print_r($includes);print_r('</pre></p>');

   get_includes(array_keys($parents[$parent]['children']),$includes,$parents);
   // print_r('<p><pre>INCLUDES: ');print_r($includes);print_r('</pre></p>');

  // Now use $includes in the args to wp_list_pages.
  $args=array(
    'title_li' => 'Tree of Parent Page ' . $parent,
    'include' => implode(",", $includes),
    'echo' => 0,
  );
  $page_nav = wp_list_pages( $args );
  // print_r(htmlentities($page_nav));print_r('<br />');
  echo $page_nav;
}

?>