Fedora Core 4 already has PHP5, Core 2 does not
The instructions you're following are for Fedora Core 4, which includes php5. Fedora Core 2 includes php4. Nothing wrong with the instructions...you're just using them on the wrong OS version.
Note that Fedora Core 2 has been end-of-lifed by Fedora. It's not a version that I would recommend deploying on new servers. That said, if you insist, it is possible to build php 5 from source on Fedora Core 2 without a whole lot of trouble (I also don't recommend having vital services installed from source--packages provided by the vendor are much easier to keep up to date--but if you need php 5 features, I guess building from source is the easiest way to get there). I'm in the midst of building php5 packages for FC3 and RHEL 3/4, and it's proving quite difficult...normally I'd recommend rebuilding the SRPM to someone in your shoes, but it's definitely not an amateur-friendly task. Building it from source is almost certainly easier.