private function _execute($args = array())
    {
        if ($this->_err) {
            return false;
        };
        if ($this->_sth) {
            if ($this->_sth->execute($args)) {
                return true;
            } else {
                $this->_err = implode(' ', $this->_sth->errorInfo());
                return false;
            };
        } else {
            $this->_err = "No statement to execute.";
        };
        return false;
    }