I wish I’d known about this online tool months ago. Who needs PhotoShop now!
This post describes how to set up a single web development environment that allows you to test the same files under PHP 4 and PHP 5 at the same time. The Windows versions of Apache and PHP are described, but the same configuration techniques can be applied to other systems.
When PHP 4 or 5 is run as an Apache 2 SAPI module, relative file paths passed to functions such as file_exists() may fail when using ob_start() to cache a page.