This is why I roll my own - VERY hard to troubleshoot how the RPM-GOD decided to build things out.
You are positive that libphp4.so was built and exists? Are you pointed to the correct location of the php.ini file?
Redhat makes some interesting decisions about which compiler to ship and the like. Caused a bunch of headaches with MySQL.
I would personally recommend either using pre-built binaries or rolling your own - axps is your friend