Hello Nuno,
Paragraph: Classes must be declared before used is no longer true. For most cases this is allowed now.
To be accurate, we solved the BC issue but for people who want to use the PHP 5 features (such as implementing interfaces), they will have to declare the class before using it.
Other notes: ext/domxml is replaced by ext/dom which is w3c dom compliant. ext/tidy was added to the default distribution and its method names were changed to studlyCaps convention.
ext/sqlite now supports an oo interface and throws exception instead of errors when that is used.
Andi