The template is designed for php5.6


This error is occurring because the framework version used for the template (https://fatfreeframework.com/3.6/home) does not support the latest php 7.2 release. You have 2 options to fix the issue:

1) use a php version less than 7.2 from your server. The template is designed for php5.6.

2) update the fat free framework version in /server side/lib/