Working with nested data and find method with breadcrumbs in CakePHP

Do you working with tree data in your projects?

Well, in CakePHP there is a Tree behavior which will help you to handle such structures. Let me show you how to use it in your projects. Hierarchical data structures are very well described here by Mike Hillyer and I would suggest you to take a look before you continue reading.

Let’s say we have following data structure:

CREATE TABLE IF NOT EXISTS `categories` (
  `id` INT(10) NOT NULL AUTO_INCREMENT,
  `parent_id` INT(10) DEFAULT NULL,
  `name` VARCHAR(255) DEFAULT NULL,
  `lft` INT(10) DEFAULT NULL,
  `rght` INT(10) DEFAULT NULL,
  PRIMARY KEY  (`id`)
)

Note, that in that table there are 3 special fields: parent_id, lft and rght.

The first one is very familiar to everyone who understanding the tree structures. The other 2 are to handle the MPTT logic (see the article mentioned above). The beautiful part of using Tree behavior is that you don’t need to worry about these 2 extra columns. The behavior will fill them automatically. 🙂

So, continue with the example. Attach the Tree behavior to your Model:

<?php
class Category extends AppModel {
    var $name = 'Category';
    var $useTable = 'categories';
    var $actsAs = array('Tree' => 'nested');
}
?>

That’s it. Now when you save (insert or update) your data into the table, the fields lft and rght will be automatically populated with the correct values. Of course your task is to have proper value set in parent_id 🙂

Why this is so important?
As you already know /if you read the article for MPTT/ using lft and rght values will give possibility to get very easy nested data in various ways.
In Model::find function there is already threaded option, but what about having breadcrumbs?

Here is a way to extend the Model::find function with this functionality. /inspired by Daniel Hofstetter’s post/

<?php
class Category extends AppModel {
    var $name = 'Category';
    var $useTable = 'categories';
    var $actsAs = array('Tree' => 'nested');

    public function find($type, $options = array()) {
        switch ($type) {
            case 'breadcrumbs':
                if(!isset($options['fields']))
                    $options['fields'] = null;
                if(!isset($options['recursive']))
                    $options['recursive'] = null;
                if(is_object($this->Behaviors->Tree) && $options['id']){
                    return $this->Behaviors->Tree->getpath($this, $options['id'], $options['fields'], $options['recursive']);
                } else {
                    return null;
                }
                break;
            default:
                return parent::find($type, $options);
        }
    }
}
?>

As you can see I am using the function TreeBehavior::getpath. There are a lot of handy functions in this behavior, but for breadcrumbs example this is just enough.

How to use it?

$this->Category->find('breadcrumbs', array('id'=>1));

so if you have data like this:

1 Root
2     Cat1
3         Cat1.1
4     Cat2

and use the function mentioned above with id=3 the result will be:

Array
(
    [0] => Array
        (
            [Category] => Array
                (
                    [id] => 1
                    [parent_id] =>
                    [name] => Root
                    [lft] => 1
                    [rght] => 8
                )
        )

    [1] => Array
        (
            [Category] => Array
                (
                    [id] => 2
                    [parent_id] => 1
                    [name] => Cat1
                    [lft] => 2
                    [rght] => 5
                )
        )

    [2] => Array
        (
            [Category] => Array
                (
                    [id] => 3
                    [parent_id] => 2
                    [name] => Cat1.1
                    [lft] => 3
                    [rght] => 4
                )
         )
)

After this with

$breadcrumbs = Set::extract('/Category/name', $result);
echo ' / '.implode(' / ', $breadcrumbs);

you will have the following result

/ Root / Cat1 / Cat1.1

I am leaving to you the styling of it as well as adding the links to the parent nodes.

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