Listing 13.2. Treść pliku lib/model/TrenPeer.php
class TrenPeer extends BaseTrenPeer {

    public static function doSelect(Criteria $criteria, PropelPDO $con = null)
    {
        $criteria = clone $criteria;
        $criteria->addAscendingOrderByColumn(self::NUMER);
        return parent::doSelect($criteria, $con);
    }

    static public function retrieveBySlug($slug)
    {
        $c = new Criteria();
        $c->add(self::SLUG, $slug);
        return parent::doSelectOne($c);
    }
}