Tree Structure using ul,li format in php - php

Question

Code for Tree structure using ul, li in php...
*In the output i am missing ul or in some place.*
I want this for checkboxes when we click the parent check box their childs must be selected and sub childs too.
<?php
$groups = array(
array('depth'=>0,'value'=>'DEF'),
array('depth'=>1,'value'=>'DEF 1'),
array('depth'=>2,'value'=>'DEF_1'),
array('depth'=>1,'value'=>'DEF2'),
array('depth'=>0,'value'=>'GROUP'),
array('depth'=>1,'value'=>'GROUP1'),
array('depth'=>1,'value'=>'GROUP2'),
array('depth'=>2,'value'=>'GROUP2_1'),
array('depth'=>2,'value'=>'TELUGU'),
array('depth'=>3,'value'=>'RAM'),
array('depth'=>0,'value'=>'GROUP3'),
array('depth'=>1,'value'=>'GROUP3_1'),
array('depth'=>1,'value'=>'GROUP3_2'),
array('depth'=>1,'value'=>'GROUP3_3'),
array('depth'=>1,'value'=>'DEF2_1'),
array('depth'=>0,'value'=>'GROUP4'),
array('depth'=>0,'value'=>'T8')
);
$count = count($groups);
$old_depth = 0;
echo '<ul>'.chr(13).chr(10);
for($i = 0; $i<$count; $i++)
{
if($old_depth==$groups[$i]['depth'])
{
echo '<li>';
echo $groups[$i]['value'];
if(isset($groups[$i+1]))
{
if($old_depth!=$groups[$i+1]['depth']){
echo '<ul>';
}
else
{
echo '</li>';
}
}
}
if($old_depth<$groups[$i]['depth'])
{
echo '<li>';
echo $groups[$i]['value'];
if(isset($groups[$i+1]))
{
if(($groups[$i]['depth'])+1==$groups[$i+1]['depth']){
echo '<ul>';
}
else
{
echo '</li>';
if(!($groups[$i]['depth']==$groups[$i+1]['depth']))
{
echo '</ul></li>';
}
if($groups[$i+1]['depth']==0)
{
echo '</ul></li>';
}
}
}
else
{
echo '</ul>';
}
}
}
echo '</li></ul>';
?>
I want the output in this format.
<ul>
<li>DEF
<ul>
<li>DEF1
<ul>
<li>DEF_1</li>
</ul>
</li>
<li>DEF2</li>
</ul>
</li>
<li>GROUP
<ul>
<li>GROUP1</li>
<li>GROUP2
<ul>
<li>GROUP2_1</li>
<li>TELUGU
<ul>
<li>RAM</li>
</ul>
</li>
</ul>
</li>
</ul>
</li>
<li>GROUP3
<ul>
<li>GROUP3_1</li>
<li>GROUP3_2</li>
<li>GROUP3_3</li>
<li>DEF2_1</li>
</ul>
</li>
<li>GROUP4</li>
<li>T8</li>
</ul>