Is this just Caddy + PHP?
But yes, from a practical standpoint, your PHP apps should _just work_ if you run it with this instead of php-fpm, provided that you aren't doing anything weird.
If you're using a modern PHP framework (e.g. Laravel, Symfony) then you can use FrankenPHP's worker mode which is a huge boost in performance by keeping workers running which have the framework already warmed up and ready to accept requests right away, instead of having to boot the framework on every request.