I try to figure out if the module
mod_expires is installed. So I created a phpinfo() site and loaded it, but there is no section called apache2handler anywhere.
In this post there is apache2handler. I am using PHP Version 5.6.39.
What you are seeing in the output of
phpinfo() is the PHP environment. Generally, you will only see a list of Apache loaded modules (an apache2handler section) if PHP itself is installed as an Apache module (eg. mod_php). PHP is often installed as CGI/FastCGI, in which case you won't necessarily be able to detect (from PHP) whether mod_expires is installed or not.