From a fresh 64-bit install of Centos 5 or RHEL 5 without Apache, PHP or MySQL packages installed:

Install Apache:

yum install httpd.x86_64 httpd-devel.x86_64

Install the latest PHP & MySQL from Remi:

wget http://download.fedora.redhat.com/pub/epel/5/i386/epel-release-5-4.noarch.rpm
wget http://rpms.famillecollet.com/enterprise/remi-release-5.rpm
rpm -Uvh remi-release-5*.rpm epel-release-5*.rpm
yum --enablerepo=remi install php php-xml
yum --enablerepo=remi install mysql-devel.x86_64 mysql-server.x86_64 \
    mysql-libs.x86_64 php-mysql

Start Apache and MySQL and you should be good to go:

/etc/rc.d/init.d/httpd start
/etc/rc.d/init.d/mysqld start

Note, if you already have the packages installed and you only wish to update to the latest versions, replace ‘install’ in the yum command with ‘update’.