PHP - fine if you want to learn yet another language. And spend 10 years using it. For everyone else there is Wordpress, Joomla (yuk) Droopl (?) etc which are supposed to be easy, but, trust me, are yet another learning curve with limitations.

And if JavaScript was so infra-dig, how come a bog-standard Fakebook page (sans apps) with Chat switched off - has 180+ JavaScript files listed?

One reason is that JS gives your PC the task of dealing with the time consuming stuff wot would load their servers. They have a lot of servers. But a lot of subscribers.

I considered using PHP for my audio website but the first hurdle was having to construct an area for every person currently playing an audio. And how many people do you cater for? Similar hurdles with server-side JS.

Answer is distributed processing. That answer is client-side. Only JS will do it on a website. That is why Fakebook could grow so fast.

There is clever and there is smart. They ain't the same.