Newsforge has a very brief article posted that talks about PHP 5 and some of the features of its "new look" from the previous version.

In July Zend Technologies announced the latest version of PHP, the widely used scripting language for Web programming. Version 5 incorporates a series of substantial enhancements over previous releases. Here's an introduction to some of the new features.

The greatest change in PHP 5 comes with a complete redesign of its object model, and with it, a tighter integration to object-oriented (OO) paradigms. [...] PHP 5 also takes a revamped approach to another pervasive technology: XML. [...] Another area which was also revised was the interaction of PHP with mainstream relational databases: MySQL and SQLite.

It's a very brief overview, glossing over a lot of the "fun stuff" that PHP 5 has included, but it's still a place to start...