How to install PHP 5.6 and 7.0 - 8.3 with PHP-FPM and FastCGI mode for ISPConfig 3.2 with apt on Ubuntu 20.04 - 24.04

When using ISPConfig, by default, you only have the main PHP version for your distribution. This guide will show you how to install additional PHP versions (5.6, 7.0, 7.1, 7.2, 7.3, 7.4, 8.1, 8.2, and 8.3) on an Ubuntu server with ISPConfig.