The difference, it seems to me, is that astro is a framework and, specifically, meant for server side generated static pages with a bit of dynamic elements in t

The difference, it seems to me, is that astro is a framework and, specifically, meant for server side generated static pages with a bit of dynamic elements in them. I don't think it is all that capable of doing highly dynamic SSR apps (though their server Islands might make that possible? https://docs.astro.build/en/guides/server-islands/ https://docs.astro.build/en/guides/server-islands/) And, also, "php" in your question could be ruby, go, C or anything else that runs on the server. I prefer htmx or, better yet, Datastar which are both small, backend agnostic, js libraries for making ssr html interactive to varying degrees. You could, in theory, use astro with them but probably better to just use something else.