Personally I find this the easiest way to get PHP5 etc installed:
Get the MySQL package from linuxpackages or a mirror.
Get the source code for Apache and PHP.
Configure and compile Apache and PHP (making sure you use all of the flags you will require for PHP like --with-mysql or --with-mysqli if you want mysql improved)
You should now have Apache and PHP both working on your system (after the mandatory httpd.conf and mod_php edits - nothing complicated there though). MySQL from the package does not start however, and this is because it hasn't been set up. So run this as root:
su mysql -c mysql_install_db
and then start MySQLd (/etc/rc.d/rc.mysqld start)
It should now start up without problems. Another thing you would be advised to do at this point would be to password the root user with this:
mysql
use mysql;
update user set Password = PASSWORD('omogfgsdfgsfg');
flush privileges;
That works for me anyway
EDIT: Oh, and just so you don't have to look if you didn't already know to get into the CLI once the password is set use 'mysql -p' instead of 'mysql'.