A tutorial on Howtoforge explains how to use apt on Debian GNU/Linux to install PHP 5.6–8.2 with PHP-FPM and FastCGI mode for ISPConfig 3.2.
How to install PHP 5.6 and 7.0 - 8.2 with PHP-FPM and FastCGI mode for ISPConfig 3.2 with apt on Debian 9 to 11
When using ISPConfig, by default, you only have the main PHP version for your distribution. This guide will take you through installing additional PHP versions (5.6, 7.0, 7.1, 7.2, 7.3, 7.4, 8.1, and 8.2) on a Debian server with ISPConfig. A similar guide is available for Ubuntu systems, which can be found here.
After installing the additional versions, you can select them for use on specific websites in both PHP-FPM and FastCGI mode.
