PayPal Payments Pro/Adaptive Payments PHP Class Library includes methods to easily integrate all of PayPal's APIs, including PayPal Payments Pro and Adaptive Payments. It makes it extremely quick and easy to tie PayPal into your applications. It comes with template solution files for nearly every API call available. All you have to do is populate the request parameters, and you'll get a PHP array result which includes everything you'll need from the API call.
CodeIgniter for PayPal Payments Pro includes every API call available in PayPal's NVP documentation, as well as their Authentication and Permissions APIs. The controller includes "template" methods for every call which include all the possible parameters which can be passed into each particular call. All you have to do is fill the blank parameters in the array templates and pass the results into the library method. An array will be returned with all of the response fields from PayPal, as well as a few extra fields for troubleshooting purposes.