<?php
/******** 120922 by cahyadsn@yahoo.com ********
-- table category
DROP TABLE IF EXISTS `category`;
CREATE TABLE IF NOT EXISTS `category` (
  `id` int(11) UNSIGNED NOT NULL,
  `parent_id`  int(11) UNSIGNED NOT NULL DEFAULT '0',
  `name` varchar(100) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;
--
-- example
--
INSERT INTO `category` (`id`, `parent_id`, `name`) VALUES
(1,0,"node no 1"),
(2,0,"node no  2"),
(3,1,"node no  1.1"),
(4,2,"node no  2.1"),
(5,3,"node no  3.1.1"),
(6,3,"node no  3.1.2");
*************************************************/
class category{
  var $mysqli;

  function __construct(){
    //--- database configuration
    $dbhost="localhost";
    $dbuser="root";
    $dbpass="";
    $dbname="test";
    //---- initiate database connection
    $this->mysqli = new mysqli($dbhost, $dbuser, $dbpass, $dbname);
    if (mysqli_connect_error()) {
      die('Connect Error (' . mysqli_connect_errno() . ') '
            . mysqli_connect_error());
    }
  }

  function hasChild($parent_id)
  {
    $sql = "SELECT COUNT(*) as count FROM category WHERE parent_id = ' " . $parent_id . " ' ";
    $rs=$this->mysqli->query($sql)->fetch_object();
    return $rs->count;
  }

  function CategoryTree($list,$parent,$append)
  {
    $list = '<li>'.$parent->name.'</li>';
    if ($this->hasChild($parent->id)) // check if the id has a child
    {
      $append++; // this is our basis on what level is the category e.g. (child1,child2,child3)
      $list .= "<ul class='child child".$append." '>";
      $sql = "SELECT * FROM category WHERE parent_id = ' " . $parent->id . " ' ";
      $obj=$this->mysqli->query($sql);
      $child=$obj->fetch_object();
      do{
        $list .= $this->CategoryTree($list,$child,$append);
      }while($child = $obj->fetch_object());
      $list .= "</ul>";
    }
    return $list;
  }
  function CategoryList()
  {
    $list = "";
    $sql = "SELECT * FROM category WHERE (parent_id = 0 OR parent_id IS NULL)";
    $obj=$this->mysqli->query($sql);
    $parent=$obj->fetch_object();
    $mainlist = "<ul class='parent'>";
    do{
      $mainlist .= $this->CategoryTree($list,$parent,$append = 0);
    }while($parent = $obj->fetch_object());
    $list .= "</ul>";
    return $mainlist;
  }
  function __destruct()
  {
    $this->mysqli->close();
  }
}

//===================
$category=new category();
echo $category->CategoryList();

?>