Updated your paypal.php
Now it will return payment price or payment failed message
Updated Phonegap Paypal plugin.
see updated example (example_phonegappaypal_advanced_verify_payment id_requires client id.capx)
and your can use PhonegapPaypal.PaymentId, PhonegapPaypal.PaymentAmount, PhonegapPaypal.PaymentCurrency, PhonegapPaypal.PaymentShortDescription, PhonegapPaypal.PaymentCreateTime in both c2 and php
And you can use "HKD" instead of "USD" in c2 event sheet, so you probably need not get_rate_cache function in php.
Thanks for your patience and kind donation.
Sang Ki Kwon