If you are just starting out as a web developer and aren't planning on changing careers anytime soon, the #1 language you should learn is JavaScript. It, or languages that compile to it, will still be in fashion in 5 or even 10 years. That's because the web is shifting to thick clients, and JavaScript is the only choice in browsers. JavaScript is also finding its way into server-side code (Node.js).
"I think PHP is the perfect language for beginning web development for two reasons: Direct HTML embedding."
Server-side view rendering is on its way out. So this is not a real advantage.
"I find it more than a little strange that PHP is simultaneously (a) out of fashion, and yet (b) absolutely everywhere."
This is simply how technologies rise and fall. By the time a technology is ubiquitous, the original problems it solved have changed and new solutions are being created. Just because you have a bunch of legacy code running lots of web apps doesn't mean it's the future--it means it's the past.
Also, why pick a language that pays poorly? Ruby is by no means inferior to PHP, and you will get paid more per hour to program in Ruby.