Centos 5.x wget [url]http://dl.fedoraproject.org/pub/epel/5/x86_64/epel-release-5-4.noarch.rpm[/url] wget [url]http://rpms.famillecollet.com/enterprise/remi-release-5.rpm sudo rpm -Uvh remi-release-5*.rpm epel-release-5*.rpm[/url]
Centos 6.x wget [url]http://dl.fedoraproject.org/pub/epel/6/x86_64/epel-release-6-8.noarch.rpm[/url] wget [url]http://rpms.famillecollet.com/enterprise/remi-release-6.rpm sudo rpm -Uvh remi-release-6*.rpm epel-release-6*.rpm[/url]
Once installed you should see some additional repo definitions under the /etc/yum.repos.d directory.
$ ls -1 /etc/yum.repos.d/epel* /etc/yum.repos.d/remi.repo /etc/yum.repos.d/epel.repo /etc/yum.repos.d/epel-testing.repo /etc/yum.repos.d/remi.repo