reload `procmgr` in container?
At the time of writing this, no. The procmgr cli that is used here is very basic.
https://github.com/paketo-buildpacks/php-web/blob/main/cmd/procmgr/main.go
It loads the processes information listed in procs.yml, starts those processes, redirects all STDOUT/STDERR, and watches for a process to exit. If one process exits, then they all exit. There's no reload capability.
If you need to reload the information in procs.yml, you'll need to reload your container.