generate nested list

<?php
/*************************
// GENERATED NESTED LIST
// created by   : Cahya DSN
// created date : 2012-09-14
**************************/
function GenerateDataArray($arr, $parent = 0)
{
    $pages = Array();
    foreach($arr as $page)
    {
        if($page['parent'] == $parent)
        {
            $page['sub'] = isset($page['sub']) ? $page['sub'] : GenerateDataArray($arr, $page['id_category']);
            $pages[] = $page;
        }
    }
    return $pages;
}

// loop the multidimensional array recursively to generate the HTML
function GenerateDataHTML($nav)
{
    $html = '';
    foreach($nav as $page)
    {
        $html .= '<ul><li>';
        $html .= '<a href="' . $page['link'] . '">' . $page['title'] . '</a>';
        $html .= GenerateDataHTML($page['sub']);
        $html .= '</li></ul>';
    }
    return $html;
}
$data=array(
array('id_category'=>1,'title'=>'Kategori 1','parent'=>0,'link'=>'#','sort'=>1),
array('id_category'=>2,'title'=>'Kategori 1.1','parent'=>1,'link'=>'#','sort'=>1),
array('id_category'=>3,'title'=>'Kategori 1.2','parent'=>1,'link'=>'#','sort'=>2),
array('id_category'=>4,'title'=>'Kategori 1.2.1','parent'=>3,'link'=>'#','sort'=>1),
array('id_category'=>5,'title'=>'Kategori 2','parent'=>0,'link'=>'#','sort'=>2),
array('id_category'=>6,'title'=>'Kategori 3','parent'=>0,'link'=>'#','sort'=>3),
array('id_category'=>7,'title'=>'Kategori 3.1','parent'=>6,'link'=>'#','sort'=>1),
array('id_category'=>8,'title'=>'Kategori 3.2','parent'=>6,'link'=>'#','sort'=>2)
);
$dataarray = GenerateDataArray($data);
echo GenerateDataHTML($dataarray);