I imagine the main reason they moved to PHP5 was not for features but simply because the PHP development team ended support for PHP 4. That means no more securi

I imagine the main reason they moved to PHP5 was not for features but simply because the PHP development team ended support for PHP 4. That means no more security fixes for version 4. This point was mentioned explicitly by WordPress. WordPress didn't end support until 3 years after PHP 4's end of life. I think that's a more than reasonable amount of time to wait before enforcing an upgrade. The fact that WordPress does not have any code that benefits from PHP 5 is undoubtedly, in part, due to its extended support for PHP 4.