This is a question you should be asking the developers of the framework you are using. Same of course goes for any PHP application you care about. Maintainers of said projects should just click here (check the user guide for details) and subscribe an email alias to their QA list (do not subscribe personal email addresses .. people move on .. go on vacation or get hit by a bus). We announce all PHP releases on this list (actually until now we have only announced RC's, but we are expanding this to also cover alpha and beta releases).
Of course that is only half the story. The idea is that these projects actually run their test suites against the release on as many platforms as they can muster and report back any issues they discover. Checking the list of changes might help when trying to determine if a change of behavior was intentional or not. The scratchpad would also help there. Every release runs the risk of BC breaks, intentional or not. Projects that want to make life easy for their users participate actively in the process of testing PHP releases. It makes the life of the PHP developers a lot easier .. and who doesn't want to make their life's easier?
Drupal 7 on PHP 5.3beta1 with MySQL:
The tests finished in 12 min 46 sec. 9616 passes, 0 fails, and 0 exceptions.
However, there might be a bug with PostgreSQL, but I was not yet able to track that down to a simple test script.
May i have more info about PostgreSQL bug please.