Just a note that if you are running a self-compiled mysql4 (perhaps made using the instructions on fedoranews) then last night's PHP update will hose your system. For me, the dependency resolution deleted mysql-server and installed the old mysql3 "mysql" package. To fix, grab the PHP SRPM, rebuild it against your mysql4 libraries and install it without letting the automatic updater get to it.
Did you install MySQL4 as an RPM? Or did you just compile the tarball and copy the files into place (perhaps with "make install")? The MySQL sources should be set up to build RPM's, so I recommend using rpmbuild as a mortal to do so.
