Scheduled for 14th September 2015, php.net will EOL PHP 5.4, meaning they will no longer supply security updates for that release. This means it's a good time to start thinking about how you want to handle it for your servers.
It's worth considering whether you can make the jump to PHP 5.6 now, as PHP 5.5 is imminently going to change to security support mode within a few weeks, and is scheduled to become EOL next June.
Webtatic will be providing backported security updates for PHP 5.4 for 1 year across RHEL/CentOS 5.11/6.6/7.1, so this will give you time to consider your options, and plan for upgrades to your servers.
Webtatic has been providing backported security updates for PHP 5.3 beyond it's php.net EOL, but will stop doing so when PHP 5.4 is EOL'd. When this happens, it will move to the Webtatic archive servers, and not be supplied as a yum repository.