The PayPal Merchant PHP SDK by PayPal allows developers to integrate the PayPal Merchant API's functions into their PHP projects and applications. This SDK requires PHP 5.2 or greater and the curl/openssl PHP extensions.
Apple this week made the Payment Request API available for Apple Pay. The W3C-developed API works in Safari 11.1 on MacOS and Safari on iOS 11.3, allowing merchants and retailers to conduct transactions through Apple Pay, rather than alternatives such as credit/debt cards or PayPal.
Smart2Pay is known as a hub for alternative payment solution providers. Its API offers access to main payment processors that aren't typically top of mind for merchants. Now, the company has launched a Mobile SDK that allows app developers to easily accept payment through WeChat and Alipay.