On line 80 of the .spec file for the latest mod_php3 package (3.0.8-1), the configure directive '--with-postgresql' is incorrect, and should be '--with-pgsql' (at least, that's what configure --help says).
This has been fixed and will be available in our next roll-out of rawhide packages that should happen within the next day or so. The version to look for is mod_php3-3.0.9-1. It can be downloaded from rawhide.redhat.com.