PHP 4.4.9 was rolled out today, and marks the end of development for PHP4. So everyone jump to PHP5, now. PHP5.3 alpha was released today and includes namespaces; a feature planned for PHP6, but apparently pulled forward.
Namespaces means the end of tortuously long class names in OO programming. There are a bunch of other new features, and some under-the-hood optimisations. The final version is due out September time.