How To Use Multiple PHP Versions (PHP-FPM & FastCGI) With ISPConfig 3 (CentOS 6.3)

Since ISPConfig 3.0.5, it is possible to use multiple PHP versions on
one server and select the optimal PHP version for a website. This
feature works with PHP-FPM (starting with PHP 5.3) and FastCGI (all PHP
5.x versions). This tutorial shows how to build PHP 5.3 and PHP 5.4 as a
PHP-FPM and a FastCGI version on a CentOS 6.3 server. These PHP
versions can be used together with the default PHP (installed through
yum) in ISPConfig.