So, I'm asking you - as an ye olde php (and laravel) guy, where would one even start? I guess node.js and expressjs is where I look first and then branch out? Also, what's with the build systems? Isn't it js?
On the client side, I personally use vue.js + webpack. It works for me. With the nicely focussed supporting libraries (vuex, vue-router, vue-resource), I find it easy to write performant, maintainable code.
I've also written a few react apps. It's basically a slightly different approach to the same problem. It's a more mature community and has better testing solutions.
Either are good bets. For a build system I prefer webpack despite the apparent complexity. It's really just a way to transform node.js module into modules you can use in the browser. Gulp is an option but if going that route I'd just use npm scripts
Overall very pleasant experience.
Edit: woops, forgot to say what I actually wanted to say! You don't need to write everything in one language. I actually abhorred that idea, and glad I found a stack that 1. doesn't need much maintenance 2. doesn't force me to spend countless hours learning about why XYZ is better than ABC and how QRT were wrong about this and that and learning 100 different new concepts and terms. I put together the stack myself, and it worked without me having to bend my programming knowledge to the particular task. There's value in this.
So I don't think you are the only one :D
It is opinionated (as in, it picks a single option; webpack instead of gulp, react instead of angular or vue), but I think it does a good job of introducing things in isolation. I ran through the tutorial a couple times after I was more familiar with things.
One language, running on a JVM on the server and compiled to JavaScript on the browser.
Both PHP and JavaScript started as ill-conceived and/or rushed-up projects that due to (different) circumstances became hugely popular, and thus, the warts and faults started to be addressed and corrected little by little.
In this "correction" process, PHP 7 is much more farther away (more advanced, more mature) than the current state of Javascript, so i'd advise to stick to PHP 7; for the front-end, if you want to explore what you could do with heavy front-ends (i.e. Single page apps), try something like ClojureScript rather than straight JS.