FuelPHP ModelPost

<?php
class Model_Post extends \Orm\Model
{
    protected static $_properties = array(
        'id',
        'title',
        'slug',
        'summary',
        'body',
        'active',
        'category',
        'created_at',
        'updated_at',
    );

    protected static $_observers = array(
        'Orm\Observer_CreatedAt' => array(
            'events' => array('before_insert'),
            'mysql_timestamp' => false,
        ),
        'Orm\Observer_UpdatedAt' => array(
            'events' => array('before_save'),
            'mysql_timestamp' => false,
        ),
    );

    public static function validate($factory)
    {
        $val = Validation::forge($factory);
        $val->add_field('title', 'Title', 'required|max_length[255]');
        $val->add_field('slug', 'Slug', 'required|max_length[255]');
        $val->add_field('summary', 'Summary', 'required');
        $val->add_field('body', 'Body', 'required');
        $val->add_field('active', 'Active', 'required|valid_string[numeric]');
        $val->add_field('category', 'Category', 'required|valid_string[numeric]');

        return $val;
    }

    protected static $_has_many = array('comments' => array(
        'model_to' => 'Model_Comment',
        'key_from' => 'id',
        'key_to'   => 'post_id',
        'cascade_save' => true,
        'cascade_delete' => false,
    ));

}