如何从PHP中获取私有属性的价值

Question

如何从以下返回数据访问总计和货币数据。我需要访问它的PayPal返回数据。

<?PHP
$amount = $sale->amount;
print_r($amount);
?>

PayPal\Api\Amount Object
(
    [_propMap:PayPal\Common\PayPalModel:private] => Array
        (
            [total] => 1.25
            [currency] => EUR
            [details] => PayPal\Api\Details Object
                (
                    [_propMap:PayPal\Common\PayPalModel:private] => Array
                        (
                            [subtotal] => 1.25
                        )

                )

        )

);