Аж 14 глав, зачитаешься: http://amp.gs/jBgck 1. Backward Incompatible Changes 2. New Features 3. Changes in SAPI modules 4. Deprecated Functionality 5. Changed Functions 6. New Functions 7. New Classes and Interfaces 8. Removed Extensions and SAPIs 9. Other Changes to Extensions 10. New Global Constants 11. Changes to INI File Handling 12. Windows Support 13. Other Changes 14. Performance Improvements