PayPal Payment Module - PHP & Yii Framework

Our company has written a flexible custom billing system on top of the Yii Framework [login to view URL] which now requires support for PayPal payments. We need a programmer who is well versed in using the Yii Framework and is an expert in strict object-oriented programming with PHP to develop our PayPal module. You will be provided with a set of example code and unit tests which you can use to verify the functionality of your module, as well as UML diagrams and details from our programmers as to the methods that must be handled by your code. Your code should be able to drop right in to our production application and function without issue. Please provide brief details of examples of your experience with Yii Framework or another strict OOP framework for PHP in your bid. You must know how to produce quality code with working unit tests; experience with PayPal's API's is a plus. Please review the attached technical documentation PDF before bidding so that you can get an idea of the methods that your code must be able to implement. Please note that we only need one-time payments for PayPal to be implemented - at this time we are not interested in the more advanced features of PayPal like subscriptions or recurring payments.