Well, tell you the truth, I dont know where PHP is installed by FC4 installation process, the only thing I know it split the installation into many different places (i.e. libriaries are placed in one /usr/lib/ directory, php.ini in /etc/ and extensions somewhere else...(real path could be different)) So, because of that, my suggestion to you download fresh .gz package from php.net, unpack it and type
./configure --help to get list of avalable paramaters. Then type
./configure and wait untill it finish, then scroll up (I see you are using Putty, which suppors scroll) and look for the features that are not enabled by default but you would like the be enable, then search for the needed paramater string from the list you've got in first step and add it to the config:
./configure --with-gd --with-somethingelse
anyways, as TheOracle said, you should look in the installation guide that you can find at php.net documentation
P.S. dont worry about messing up the system, untill you run "make install" nothing will be moved out of the source directory

and you can experiment
P.P.S. before each run
./configure script, run
make clean otherwise it will use previously cached configs.
Good luck.