protected function errorHandler($errno, $errmsg, $errfile = '', $errline = 0)
    {
        $notice = 'Connection failed.';
        $this->setError(
            $notice,
            $errmsg,
            (string) $errno
        );
        $this->edebug(
            "$notice Error #$errno: $errmsg [$errfile line $errline]",
            self::DEBUG_CONNECTION
        );
    }