Database Abstraction

<?phpclass DataHelper{    private $dbh = null;    public __construct($dsn = '') {        if (is_empty($dsn)) {            $dsn = "some default connex string";        }    }    public connect() {        if (is_null($this->dbh)) {            $this->dbh = DB::connect($dsn);        }        if (PEAR::isError($this->dbh)) {            throw new Exception($this->dbh->getMessage());        }    }    public query($queryString, array $params = array())    {        // code    }}