Yes and no, php didn’t give you any tools to manage this, most people writing php sites back in the day (including myself) were writing js that was coupled to a specific markup yet was maintained separately. This didn’t scale well.

Then along came libraries like mootools, knockout, etc all the precursors of react, then react changed the game around encapsulation of markup and code into one place, and straightforward data flow.

SPAs were inefficient so server side rendering of js became ubiquitous, islands are a further optimisation of ssr.

This hasn’t happened in a vacuum, if you look at modern php frameworks like inertia they have a lot more in common with Astro than they do the good old 90s php