Clase php para jerarquizar mediante nidos

gistfile1.txt

<?php
//---------------------------------------------------------------------------------------------------
// Proyecto: jerarquia
// Archivo: class/nodo.php
// Tipo: definicion de clase
// Desarrolladores: Juanan Ruiz (juanan@us.es) y jjmc@us.es
//---------------------------------------------------------------------------------------------------
// Descripcion: lista, crea, borrar y edita nodos (falta mover nodos)
//---------------------------------------------------------------------------------------------------
class nodo extends ADOdb_Active_Record
{
  var $_table = 'DE_nodo';
  function listar()
  {
    $db = $this->DB();
    $query ="SELECT COUNT(parent.id) - 1 as dep , node.alias AS alias, node.lft as izq, node.rgt as der, node.id as id
      FROM DE_nodo AS node,
      DE_nodo AS parent
      WHERE node.lft BETWEEN parent.lft AND parent.rgt
      GROUP BY node.id
      ORDER BY node.lft";
    $lista = $db->getall($query);
    return $lista;
  }
function crear_hermano($id,$alias,$descripcion)
  {
    $db = $this->DB();
    $query0 = "LOCK TABLE DE_nodo WRITE";
    $query1 = "SELECT @myRight := rgt FROM DE_nodo WHERE id = $id";
    $query2 = "UPDATE DE_nodo SET rgt = rgt + 2 WHERE rgt > @myRight";
    $query3 = "UPDATE DE_nodo SET lft = lft + 2 WHERE lft > @myRight";
    $query4 = "INSERT INTO DE_nodo (alias, descripcion,lft, rgt) VALUES ('$alias','$descripcion', @myRight + 1, @myRight + 2)";
    $query5 = "UNLOCK TABLES";

    $db->StartTrans();
    $db->Execute($query0);
    $db->Execute($query1);
    $db->Execute($query2);
    $db->Execute($query3);
    $db->Execute($query4);
    $db->Execute($query5);
    $db->CompleteTrans();
  }
function crear_hijo($id,$alias,$descripcion)
  {
        $db = $this->DB();
        $query0 = "LOCK TABLE DE_nodo WRITE";
        $query1 = "SELECT @myLeft := lft FROM DE_nodo WHERE id = $id";
        $query2 = "UPDATE DE_nodo SET rgt = rgt + 2 WHERE rgt > @myLeft";
        $query3 = "UPDATE DE_nodo SET lft = lft + 2 WHERE lft > @myLeft";
        $query4 = "INSERT INTO DE_nodo (alias, descripcion,lft, rgt) VALUES ('$alias','$descripcion', @myLeft + 1, @myLeft + 2)";
        $query5 = "UNLOCK TABLES";
        $db->StartTrans();
        $db->Execute($query0);
        $db->Execute($query1);
        $db->Execute($query2);
        $db->Execute($query3);
        $db->Execute($query4);
        $db->Execute($query5);
        $db->CompleteTrans();
  }

}
?>