Running Sympl 10 on a Mythic Beasts Raspberry Pi 4, with Raspberry Pi OS Buster.
I have a few non-critical Wordpress sites on this server - noo webmail or anything else. Everything seems to be functioning smoothly on auto-pilot, so I’m not inclined to fiddle for no good reason.
However - the installed version of PHP is 7.3, which my Wordpress installations insist that I should update immediately.
The upgrade to PHP 8.0 is straightforward - but before I do it I want to reassure myself that I won’t break anything in Sympl 10. I don’t know how I would look for dependencies.
Can anyone here point me in the right direction?
Cheers 
Hello, and welcome to the Sympl forum.
I’ve had similar complaints from a Joomla! user. The concern is security vulnerabilities, and Wordpress is simply going by the PHP version number and assuming it’s the upstream Wordpress 7.3. Debian (and hence Raspberry Pi OS) keeps up with security fixes on PHP, so it should be safe, but functionally it’s still PHP 7.3 and reports its version number as such, and WP doesn’t know the difference. It’s very unlikely that WP is actually using new language features in WP8 - that would break far to many installations.
PS can you not upgrade to a Debian 11 “Bullseye” based Pi OS and Sympl?
That would give you PHP 7.4, at least a step in the right direction.
Welcome, @devbold!
As @Anahata mentioned, WordPress isn’t great at understanding that security fixes exist and are back-ported when relevant to Debian (and therefore Raspbian) packages, so it’s just assuming that PHP 7.3 isn’t going to get any security fixes, simply as the PHP developers themselves have stopped working on it.
WordPress seems to have gotten worse about this recently, even though they still officially support PHP 5.6 in WordPress core (although I suspect many recent plugins would complain), and provide security fixes themselves for WordPress 3.7 from 2013.
WordPress themselves consider support for both PHP 8.0 and 8.1 as being in ‘beta’, so you’re more likely to run into issues upgrading to that, especially with older plugins and themes.
They also mention significant speed improvements with an upgrade, but these are only between 5.6 and 7.0, and there’s not anything really notable with versions after that.
Short version: You don’t need to upgrade, and assuming you have ‘sympl-updater’ installed, you’ll automatically get security fixes so you can hide the warning.