This is why I build my personal projects in PHP even though I'm not really a fan. I use PHP and JQuery. It'll work basically forever and I can come back to it in 15 years and it'll still work.
It's still great for a lot of things. It's not necessary now but you still write way less code with it and it's got a ton of functions that there are no implementations of in the browser.
Plus you basically get it for free because it's browser cached because 75% of the sites out there are using it.