With a PHP project, you have to make all the decisions yourself, which framework (Symfony, Laravel, etc.), how to structure things, whether you can use JSX-like syntax (you can’t, really), how to handle HTML escaping safely, and how to optimise images during build time. You can use Unpic in Laravel (The Unpic creator, also former Netlify employee is now on Astro team).

https://unpic.pics/

I'm aware there's a new PHP web framework that's somewhat similar to Astro, but I can't recall the name.

Astro gives you sensible defaults out of the box. It’s designed for modern web development, so things like partial hydration, automatic image optimisation, and using components from different frameworks just work.

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/)

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.

It’s actually a lot like php, just without the php language stuff.

It’s php for javascript devs?

PHP needs to be hosted on a server that can parse PHP. Astro generates HTML so can be hosted anywhere that can serve HTML.