Category tree structure select box in cake php

########################
# Created By : Rahul Dev Xarma
# private function of this class will be use for showing category list in tree structure.
# With selectLeader($id = 0) function
########################
function __display($pid,$level)
{
global $res;
$blank = "";

for($i=0; $i< $level; $i++)
$blank .= "-";

$parents = $this->Category->find('all' , array('conditions' => array('Category.parent_id' => $pid)));

if(!empty($parents))
$level++;

foreach($parents as $value)
{
$res[$value['Category']['id']] = $blank.$value['Category']['name'];
$this->__display($value['Category']['id'],$level);
}
}


########################
# Created By : Rahul Dev Xarma
# This function will be use for showing category list in tree structure
# __display($pid,$level)
########################
function selectLeader($id = 0)
{
global $res;
$level = 0;
$parents = $this->Category->find('all',array('conditions' => array('Category.parent_id' => $id)));
$i = 0;
foreach($parents as $value)
{
$level = 0;
$res[$value['Category']['id']] = $value['Category']['name'];
$this->__display($result['categories_id'],0);
}
return $res;
}