PHP 5.3 introduced many new features and improvements including:
- Performance improvements with up to 40% faster speeds on Windows and 5-15% overall.
- New error reporting levels, garbage collection, and the MySQLnd native driver.
- Backwards compatibility changes like deprecated EREG functions and magic methods requirements.
- Namespaces, late static bindings, closures/lambdas, the __callStatic magic method, and get_called_class().
- Additions to the SPL like new iterators, the date/time object, and new constants like __DIR__ and __NAMESPACE__.