As an anecdote - in my circles I observe that PHP is very popular among people who started working in web ~2000, while ruby is popular among those who started in ~2007. Nothing to do with seniority etc, I think it's simply the default choice of whatever was in vogue at the time when the person started hacking, and by now many PHP guys skew older and are out of the startup game (i.e. working in established companies on established products).
As another example, I'm still astonishingly productive with PHP for backend APIs and rapid development projects. The symfony/Doctrine community has done a phenomenal job at bringing world-class tools to the language.
As a young person, when I was examining possible choices for development, I chose what was fast and stable. At the time that was C & PHP, and maybe even perl.
I don't see how the young people of today decide to go with Ruby, with it's terrible performance, and especially last year with it's slew of vulnerabilities. If you like the beauty of Ruby, use it on your own stuff or for learning. But using it with intention for a production environment? I just don't get it...
It's not Ruby. It's Rails. Ruby on its own is just a slightly more flexible Python.
Rails was embraced because it provided a clear way to write DB-driven web apps with minimal configuration, following a strict pattern. And a lot of people sort of like strict.
I started out with PHP in ~2000 as that's what people used, but then migrated over to Python around 2007 and web.py. Now I've experimented with node and Go, Java and Scala, but I prefer Python and Django. There's so much that Django gives you, it feels stupid not to use it. I haven't tried Ruby or Rails, I just don't feel like I need to.
It doesn't really matter what you use if it gets the job done.
As another example, I'm still astonishingly productive with PHP for backend APIs and rapid development projects. The symfony/Doctrine community has done a phenomenal job at bringing world-class tools to the language.