Question

Is it possible to represent the fifth normal form in PHP ActiveRecord?

i.e.

Person <=> (person_id) person_phone (phone_id) <=> Phone

Answer 1

The fifth normal can be represented with “$has_many through”

http://www.phpactiverecord.org/projects/main/wiki/Associations

has_many through (many to many)

This is a convenient way to configure a many-to-many association. 

In this example an order is associated with users by going the
its payments association.

 1 class Order extends ActiveRecord\Model {
 2   static $has_many = array(
 3     array('payments'),
 4     array('users', 'through' => 'payments')
 5   );
 6 }
 7 
 8 class Payment extends ActiveRecord\Model {
 9   static $belongs_to = array(
10     array('user'),
11     array('order')
12   );
13 }
14 
15 class User extends ActiveRecord\Model {
16   static $has_many = array(
17     array('payments')
18   );
19 }
20 
21 $order = Order::first();
22 # direct access to users
23 print_r($order->users); # will print an array of User object

I found the answer here:

You could create a model for the joint table, and then associate the phone table through the join table!

http://www.phpactiverecord.org/boards/4/topics/226

Also found this:
http://svn.phpontrax.com/wiki/ActiveRecordTableAssociations