function get_menu_path($curmenu=0)
 {
 static $cattree;
 $qchildextr="SELECT title, nest_under, id FROM таблица WHERE id='$curmenu';";
 $schildextr = mysql_query($qchildextr);
 $num_child = mysql_num_rows($schildextr);
 if ($num_child>0)
  {
   while (list($title, $nest_under) = mysql_fetch_row($schildextr))
    {
      $cattree .= "$title > ";
      get_menu_path($nest_under);
    }

  }
  mysql_free_result($schildextr);
  return "$cattree";
 }

echo (get_menu_path(2));

echo (get_menu_path(2));
echo (get_menu_path(4));