While there aren't many cases where you should run PHP as a daemon or cron job, there are _some_. Like, for example, you've got dozens of models and helpers written in PHP and you want to use them in queue workers or aggregation jobs.

I've run into these a few times and acquired a bit of mastery of PHP's PCNTL, POSIX and Semaphore/SHM/IPC extensions.

I don't do much PHP work anymore, but I do maintain an OSS library for other people in that situation: PHP Simple Daemon -- https://github.com/shaneharter/PHP-Daemon

This is half-plug, half +2 to your point.