Frameworks compatibility checks is an uncharted territory. The fast pace of modern release requires automation to keep up with the API description : new classes, methods and arguments, and sunsetting ones. We introduce the PDFF archive : PHP Document File Format. It provides an encyclopedic description of any PHP API, OOP or not. Static analysis tools take full advantage of this knowledge base to identify discrepancies. PDFF is both machine and human friendly,and it includes future versions.