There may be no guarantee that `$caller[...]` is actually set, or that
either `file` or `line` are not empty.

Marius Burkard authored Mar 19, 2022 and Gwyneth Llewelyn committed Mar 19, 2022

Good point; I'd even use `!empty($caller['file']) && !empty($caller['line'])` to save a few cycles in the (improbable) case where both _may_ be set, but empty (thus making the whole exercise pointless...).

Also, tried to clean up the code formatting according to the guidelines
_and_ added (most) entries for PHPDoc.

SSLProxyEngine is neither needed for http(s) redirects nor for non-SSL proxy configs.
Thus excluding it from these cases.

Based on a fix by Thom <thom@amsterdamtech.nl>

Add Debian 11 (Bullseye) to OS detection code in ISPConfig and update config for Debian testing (Sid)