[CentOS] php4/php5

Hey Guys,

I need to run PHP4/PHP5 from the same physical server.
I have apache + php5 currently.
Im thinking of creating a new apache and php4 from srpms and installing
It all in say /opt/apache_php4 and then running it from its own IP since
The server has two external IP addresses available.

Just wondering if anybody here has needed to do the same in the past and
what did you do to achieve running them both from the same server?

Thanks,
 Wayne