Sometime you may need to form a tree structure from the values of the database table. For Ex- You may need to form a hierarchy of categories and subcategories like this:

My Categories

    Fun
        Sport
            Surfing
            Extreme knitting
        Friends
            Gerald
            Gwendolyn
    Work
        Reports
            Annual
            Status
        Trips
            National
            International

This can be easily achieved by cakephp's tree behavior

Requirement: For this purpose you need 3 column in the database table

1) parent : int  type
2) lft int type
3) rght - int</p>

CREATE TABLE categories (
    id INTEGER(10) UNSIGNED NOT NULL AUTO_INCREMENT,
    parent_id INTEGER(10) DEFAULT NULL,
    lft INTEGER(10) DEFAULT NULL,
    rght INTEGER(10) DEFAULT NULL,
    name VARCHAR(255) DEFAULT '',
    PRIMARY KEY  (id)
);

INSERT INTO `categories` (`id`, `name`, `parent_id`, `lft`, `rght`) VALUES(1, 'My Categories', NULL, 1, 30);
INSERT INTO `categories` (`id`, `name`, `parent_id`, `lft`, `rght`) VALUES(2, 'Fun', 1, 2, 15);
INSERT INTO `categories` (`id`, `name`, `parent_id`, `lft`, `rght`) VALUES(3, 'Sport', 2, 3, 8);
INSERT INTO `categories` (`id`, `name`, `parent_id`, `lft`, `rght`) VALUES(4, 'Surfing', 3, 4, 5);
INSERT INTO `categories` (`id`, `name`, `parent_id`, `lft`, `rght`) VALUES(5, 'Extreme knitting', 3, 6, 7);
INSERT INTO `categories` (`id`, `name`, `parent_id`, `lft`, `rght`) VALUES(6, 'Friends', 2, 9, 14);
INSERT INTO `categories` (`id`, `name`, `parent_id`, `lft`, `rght`) VALUES(7, 'Gerald', 6, 10, 11);
INSERT INTO `categories` (`id`, `name`, `parent_id`, `lft`, `rght`) VALUES(8, 'Gwendolyn', 6, 12, 13);
INSERT INTO `categories` (`id`, `name`, `parent_id`, `lft`, `rght`) VALUES(9, 'Work', 1, 16, 29);
INSERT INTO `categories` (`id`, `name`, `parent_id`, `lft`, `rght`) VALUES(10, 'Reports', 9, 17, 22);
INSERT INTO `categories` (`id`, `name`, `parent_id`, `lft`, `rght`) VALUES(11, 'Annual', 10, 18, 19);
INSERT INTO `categories` (`id`, `name`, `parent_id`, `lft`, `rght`) VALUES(12, 'Status', 10, 20, 21);
INSERT INTO `categories` (`id`, `name`, `parent_id`, `lft`, `rght`) VALUES(13, 'Trips', 9, 23, 28);
INSERT INTO `categories` (`id`, `name`, `parent_id`, `lft`, `rght`) VALUES(14, 'National', 13, 24, 25);
INSERT INTO `categories` (`id`, `name`, `parent_id`, `lft`, `rght`) VALUES(15, 'International', 13, 26, 27);

Write the following in controller:

<?php
class CategoriesController extends AppController {

        var $name = 'Categories';

        function index() {
                $this->data = $this->Category->generatetreelist(null, null, null, '&nbsp;&nbsp;&nbsp;');
                debug ($this->data); die;
        }
}
?>

and in the model:

<?php
// app/models/category.php
class Category extends AppModel {
    var $name = 'Category';
    var $actsAs = array('Tree');
}
?>