How to run PHP4 and PHP5 side-by-side

Hello, I'm using Apache 2.0 on a Linux box and I'm trying to figure out how to run PHP5 (beta2) and PHP4 co-existantly. I have compiled both of them with --enable-versioning, but I can't figure out what I need to put in my httpd.conf to make it differentiate the two versions. Ideally I would like php5 to be enabled for certain virtualhosts, and php4 for others. But using .php5 file extensions would be acceptable too. I have compiled PHP4 and PHP5 with the following configure options: './configure' '--with-apxs2=/home/httpd/bin/apxs' '--with-mysql=/home/mysql' '--enable-track-vars' '--enable-versioning' Thanks in advance -Adam