1.paypal html变量的定义

https://developer.paypal.com/docs/classic/paypal-payments-standard/integration-guide/Appx_websitestandard_htmlvariables/#shopping-cart-variables

2 paypal国别代码

https://developer.paypal.com/docs/classic/api/state_codes/

3.paypal 支持的货币代码

https://developer.paypal.com/docs/classic/api/currency_codes/#id09A6G0U0GYK

4 paypal 关于地址的文档

https://developer.paypal.com/docs/classic/paypal-payments-standard/integration-guide/html_example_installment/?mark=address

5 购物车示例代码