I just visited the php docs, and it seems that they have replaced the instructions with "find a php package for your distro...). Not very comforting.
My advice...unpack the source. Read the INSTALL file. Run "./configure --help" - this will show you all available configure options. You can adjust them or leave them at their defaults which are usually reasonable. One thing, to work with apache you need mod_so.c built into apache or you can't use the php dynamic module. You can check using "httpd -l", and you should see:
Then you can just run:
./configure --with-mysql --with-apxs && make install
Read the INSTALL file, it really does have everything you need. I personally recommend using the dynamic module rather than the static one (there is instructions for both).
Good luck, let us know if you have problems.