The Coinbase PHP SDK by Coinbase allows integration with the API, providing bitcoin features to application development projects. Includes installation with composer, authentication with Api Key, and authorization with OAuth2. By Jori Lallo.
Xchangeonline is a tool that provides currency conversion and rounding functionality that can be integrated with other applications. Their selling point is that, unlike other currency conversion tools available, their service is easy for anyone to use, reliable and affordable. The Xchangeonline API makes it possible for third party developers to access this functionality.