Most companies out there, when working with online tools and scripting, have two servers for their people to work on - a production server and a development server. The ideal setup is that both would be as similar as possible and you could port an app over from one to the other with no hesitation.

Well, unfortunately, due to some of the constraints of finances and upkeep time, this just isn't always the case - so you end up developing on the same server that your production programs are on. Now, this is all well and good, but what about your PHP install? If you're running it as a module, chances are, all of your sites would be affected if you got a bad compile in. Well, this article from PHPBuilder.com offers some helpful hints on running a few different instances of PHP on the same machine.

The way that they suggest doing things is to have them run as a CGI install, and just point to different versions of the PHP-CGI binary in your scripts. It's an interesting way to go about it, but you'd think there'd be an easier way than to have to track which CGI to use for which files and what features each one has. Personally, I'm more for just setting up another Apache instance, even on the same machine, and working off of a clean PHP install on that one, rather than running them as a CGI.