abstract class Base {
    protected $_dbConnection;

    public function setDbConnection(\Doctrine\DBAL\Connection $dbConnection){
        $this->_dbConnection = $dbConnection;
    }

    public function getDbConnection(){
        return $this->_dbConnection;
    }

    abstract function calculateRisk($params);
}

class MarketFund extends Base {

    public function __construct()
    {
        $this->_dbh = parent::getDbConnection();
    }
}

new MarketFund(); // <-jak to wywolac prawidlowo by przekazalo parametry polaczenia do bazy ??