On the first page of the description, we have installed a version of PHP 5.6.40 as an optional version of PHP for the Debian 9 (Stretch) based perfect server, which will be available in FastCGI and PHP-FPM modes. On this page of the description, we make the subsequent settings of the installed PHP system and add them to the optional PHP versions in the ISPConfig3 control panel.

In this tutorial we will install PHP 7.1.19 on the perfect server environment with ISPConfig on Debian 8. PHP is installed in optional mode, so it is available for web hosts in PHP-FPM and FastCGI modes, in addition to the default version of 5.6.x. (Page 2 of the description)