Upgrading PHP on CentOS 6.5 (Final)

For CentOS 6, PHP 5.3.3 is the latest version of PHP available through the official CentOS package repository. Keep in mind, even though PHP 5.3.3 was released July 22, 2010, the official CentOS 6 PHP package was updated November 24, 2013. Why? Critical bug fixes are backported. See this question for more information: "Why are outdated packages installed by yum on CentOS? (specifically PHP 5.1) How to fix?"

If you'd like to use a more recent version of PHP, Les RPM de Remi offers CentOS PHP packages via a repository that you can add to the yum package manager. To add it as a yum repository, follow the site's instructions.

Note: Questions of this variety are probably better suited for Server Fault.

As Jacob mentioned, the CentOS packages repo appears to only have PHP 5.3 available at the moment. But these commands seemed to work for me...

rpm -Uvh http://mirror.webtatic.com/yum/el6/latest.rpm
yum remove php-common       # Need to remove this, otherwise it conflicts
yum install php56w
yum install php56w-mysql
yum install php56w-common
yum install php56w-pdo
yum install php56w-opcache
php --version               # Verify version has been upgraded

You can alternatively use php54w or php55w if required.

CAUTION!
This may potentially break your website if it doesn't fully resolve all your dependencies, so you may need a couple of extra packages in some cases. See here for a list of other PHP 5.6 modules that are available.

If you encounter a problem and need to reset back to the default, you can use these commands:

sudo yum remove php56w
sudo yum remove php56w-common
sudo yum install php-common
sudo yum install php-mysql
sudo yum install php

(Thanks Fabrizio Bartolomucci)