I have been coding php for a while now, but I just discovered how to setup a test environment on a win98 machine. Please no flames about the mirosoft junk. I would love to switch to linux completely, but unfortunately I need a dual boot since most of my work is in a windows environment. Anyway, here are the details. This was super easy to setup, and only required 2 steps.
1. Download and install Omni HTTPD. You can get this from tucows.com or any other download site. Upon installing v2.06, there is a option for installing php 4.0! After this simple installation, php and the webserver are now installed.
2. Download and install mysql. Follow the installation instructions for installing in winNT, but start 'mysqld --standalone' instead of 'mysqld --install'.
Thats it. I was amazed at how super easy it was. I feel stupid for not doing this earlier. This also runs great at my home network. I can easily develop intranet apps at home now.