many-to-many relationship on kohana 3.2 - php

Question

I've got some trouble trying to make this work. I have 2 models, User_Pro and Category. I read the relationships documentation on kohana guide and I understand i need to define a $_has_many relationship on the User_Pro and Category models and create the model user_pro_categories with the belongs_to field.
User_Pro model:
protected $_has_many = array(
'categories' => array(
'model' => 'TM_Category',
'through' => 'user_pro_categories',
'foreign_key' => 'id_user_pro',
),
);
Category model:
protected $_has_many = array(
'users_pro' => array(
'model' => 'TM_User_Pro',
'through' => 'user_pro_categories',
'foreign_key' => 'id_category',
),
);
user_pro_categories model:
protected $_belongs_to = array(
'user_pro' => array(
'model' => 'TM_User_Pro',
'foreign_key' => 'id_user_pro',
),
'category' => array(
'model' => 'TM_Category',
'foreign_key' => 'id_category',
),
);
The error I'm getting is:
Database_Exception [ 1054 ]: Unknown column 'tm3_user_pro_categories.category_id' in
'on clause' [ SELECT `tm3_tm_category`.* FROM `tm3_categories` AS `tm3_tm_category` JOIN
`tm3_user_pro_categories` ON (`tm3_user_pro_categories`.`category_id` = `tm3_tm_category`.`id_category`)
WHERE `tm3_user_pro_categories`.`id_user_pro` = '2' ]
It's like it doesn't care about the fk's i defined and it want's to use the suffix thing... any idea?

Answer 1

Here is the example to give you quick idea how Kohana ORM works. And wish it will be helpful for others too.
Student Model
<?php defined('SYSPATH') or die('No direct script access.');
class Model_Student extends ORM {
protected $_primary_key = 'idstudent'; // take a look
protected $_has_many = array(
'courses'=> array(
'model' => 'course', // Course model
'through' => 'students_courses', // many-to-may through
'far_key' => 'id_for_course', // "column name" relating to the Course Model in "students_courses" table
'foreign_key' => 'id_for_student' // "column name" relating to the Student Model in "students_courses" table
),
);
}
Course Model
<?php defined('SYSPATH') or die('No direct script access.');
class Model_Course extends ORM {
protected $_primary_key = 'idcourse'; // take a look
protected $_has_many = array(
'students'=> array(
'model' => 'student',
'far_key' => 'id_for_student',
'through' => 'students_courses',
'foreign_key' => 'id_for_course'
),
);
}
SQL Script
CREATE TABLE IF NOT EXISTS `students` (
`idstudent` int(10) unsigned NOT NULL AUTO_INCREMENT,
`name` varchar(45) DEFAULT NULL,
PRIMARY KEY (`idstudent`)
) ENGINE=MyISAM;
INSERT INTO `students` (`idstudent`, `name`) VALUES
(1, 's1'),
(2, 's2');
/* column idcourse and PR idcourseS ? */
CREATE TABLE IF NOT EXISTS `courses` (
`idcourse` int(11) NOT NULL,
`name` varchar(45) DEFAULT NULL,
PRIMARY KEY (`idcourse`)
) ENGINE=MyISAM;
INSERT INTO `courses` (`idcourse`, `name`) VALUES
(1, 'c1'),
(2, 'c2'),
(3, 'c3');
CREATE TABLE IF NOT EXISTS `students_courses` (
`id_for_student` int(10) unsigned NOT NULL,
`id_for_course` int(10) unsigned NOT NULL
) ENGINE=MyISAM;
INSERT INTO `students_courses` (`id_for_student`, `id_for_course`) VALUES
(1, 1),
(1, 3);
$student = new Model_Student(1);
$courses = $student->courses->find_all();
echo Debug::vars($courses);
foreach($courses as $course) {
echo Debug::vars($course->object());
}
Running code above will create following SQL query.
SELECT `course`.* FROM `courses` AS `course` JOIN `students_courses` ON (`students_courses`.`id_for_course` = `course`.`idcourse`) WHERE `students_courses`.`id_for_student` = '1'

Answer 2

You don't need to create a model for pivot table for many-to-many relationship. Just define the through option in both models, make sure your primary/foreign keys follow Kohana convention and you're ready to go. Below example from Kohana ORM User and Role models:
class Model_User
{
protected $_has_many = array(
'roles' => array('model' => 'role', 'through' => 'roles_users'),
);
}
class Model_Role
{
protected $_has_many = array(
'users' => array('model' => 'user', 'through' => 'roles_users')
);
}