Thanks Joe, that one works! Here's for everybody else who has difficulty getting this PHP \"update\" to work:

Shutdown RW if you haven't already done so
Goto '/Applications/RapidWeaver.app/Contents/MacOS'
rename php to php.bak (or php.original)
copy the downloaded php file to '/Applications/RapidWeaver.app/Contents/MacOS'
In case the file downloaded as php.bin, rename it to php
Double click on the 'new' php file. You'll receive and error message, just click 'Done'
Go to macOS' System Settings > Privacy & Security to review security information for software before allowing it to run.
To adjust how aggressive Gatekeeper is, click the menu next to 'Allow applications from' and choose either 'App Store' to only allow apps downloaded from the App Store or 'App Store & Known Developers' to allow both App Store apps and signed apps distributed outside the App Store. With the latter option enabled, signed apps will still produce a warning to let the user know they’re trying to open the app downloaded from the internet, but you can dismiss it by hitting 'Open' to continue launching the app. Unsigned non-App Store apps must be manually allowed using the above method.
Allow the blocked app underneath the Security heading at the bottom of the Privacy & Security section. Click 'Open Anyway', then confirm by clicking 'Open' again to bypass Gatekeeper.
Start RW... BLANK! Do not open a project!
Go to to Advanced settings (3rd item in left pane)
If you do NOT see 'Currently running on http://127.0.0.1:52695/' (or any other number instead of 52695), click 'Restart Webserver'
Check if you now see 'Currently running on http://127.0.0.1:52695/' (or any other number instead of 52695). If it's NOT running, then click 'Restart Webserver'. Still NOT running? Restart RW. Even now NOT running? You might want to recheck macOS' System Settings > Privacy & Security if there's, again, a blocked app to allow.
Now open a Stacks project and try it out, for example with Joe's Server Info stack. You should see running PHP 8.2.9!
Enjoy!

Hack to update PHP of RW?