I've followed the tutorial How to install PHP 7.1, 7.2 and 5.6 as PHP-FPM & FastCGI for ISPConfig 3 on Debian 9.pdf When I create a website with PHP-FPM and php 5.6, I get: ERROR 503 - Service Unavailable! I can't understand why. When I create the same website with Fast-CGI and php 5.6 and using phpversion, I get a correct answer: Version PHP courante : 5.6.33. Unfortunately I need PHP 5.3 and PHP 5.4 in the same ISPconfig configuration. Is there a tutorial to install these versions ?