Menu recursivo com php e MySQLi

function menu()
  {
    global $dbc;

  $result = $dbc->prepare('SELECT page, linktext, visable, parent FROM content WHERE visable > 0 ORDER BY parent,sort ASC');
  $result->execute();
  $result->bind_result($menu_page, $menu_linktext, $menu_visible, $menu_parent);

  while($result->fetch())
    {
        if($menu_parent == 0) $menu[$menu_page]=$menu_linktext;
        elseif(!empty($menu[$menu_parent])) $sub[$menu_parent][]=$menu_linktext;
    }

  $result->close();

  if(!empty($menu))
    {
        echo '<ul class="sf-menu" id="nav">';
        foreach($menu as $page=>$link)
          {
              echo "<li><a href='$link'>$link</a>";
              if(!empty($sub[$page]))
                {
                    echo '<ul>';
                    foreach($sub[$page] as $lnk) echo "<li><a href='$lnk'>$lnk</a></li>";
                    echo '</ul>';
                }
              echo '</li>';
          }
        echo '</ul>';
      }