Imports are also updated the moment you update the imported file.

I'm not sure if PHP stores any compiled binary or byte-code at all. Maybe it compiles it all on each request. It's super fast though, even with tons of imports.

My guess would be that it keeps compiled versions of each file in memory and on each request, it walks down the whole import path. And when it encounters a changed import, it compiles only that one.

Would be cool if someone with more knowledge could shed a light on what is actually happening.

Afaik, PHP can have opcode caching enabled or disabled.

True. I see a "Zend OPcache" section in my phpinfo().

It says:

    Cache hits   4746528
    Cache misses   38875

Both values go up every time I execute phpinfo().

I wonder why. Shouldn't "Cache misses" only go up when a source file is changed?

AFAIK, before PHP even accesses opcache for bytecode, it checks the file's metadata (last modified, most likely). So an updated file might never trigger a cache hit or miss.

If it does not access the opcache, against what is it checking the last modified date?

If you're talking about importing third party dependencies, composer takes care of that.

In PHP, dependencies are just .php files just like your own code, it all works the same.

PHP code is also typically far less complex than Python modules - modern PHP code consists of a single index.php with procedural code, and everything else is just class / function definitions, so there are no side effects.

Most major PHP frameworks like laravel, symfony, Drupal, Magento develops all kinds of complex caching layers to work around PHP's stateless 1 request/1 execution model, essentially poorly recreating shared application state you would get for free with a long running worker process.

Python's import model is not without its flaws either, but at least you have a working application state, no need to fully initialize your app for every single request.

For simple apps that are contained within a few files, PHP is hard to beat for simplicity and speed.