That’s not accurate on CentOS 7. PHP 5.4 shipped as the stock version of PHP and it will be maintained by the RHEL/CentOS devs for the life of that version of the OS.
Any package that is part of the CentOS 7 OS repos will be supported for the life of the distribution (but others from third party repos, including EPEL, SCL, etc. likely will not be…PHP 5.4 is the most certainly supported PHP version you can get on CentOS 7).
PHP 5.4 end-of-life date is September 14, 2015. You can find this information on the PHP site, here. Beside the release cycle of PHP, you should also consider the life cycle of the base OS you are using. As an example, PHP 5.3 on RHEL/CentOS 6 will be supported with security fixes by RedHat/CentOS until Nov 30, 2020.
CentOS/RHEL maintain every package they ship as part of the OS for the entire life of the OS. That’s why we like CentOS/RHEL. That’s the primary benefit of it. You can know, with reasonable confidence, that anything you deploy today will continue to work throughout the life of the OS without modification.
This is not specific to PHP, but it also applies to PHP. It has nothing to do with the PHP developers; their end-of-life notices have nothing to do with what Red Hat does. The software is Open Source, anyone can maintain it and release security patches and bugfixes, and Red Hat has built their business on doing just that. That’s the point of a long-life distribution like RHEL.