[neurostimulant]

It's pretty simple really. With php, your php sites consist of some php files that will be run by a webserver (apache, php-fpm, etc). When the webserver receive a http request, it will executes a php file that matched the request url, pass it the request body as input and send back the output as request response. On other languages, your app is typically deployed as the webserver itself, handling request directly (or indirectly with a reverse proxy in front of it) without executing any external process or terminating after each request.

The php model is simpler and easy to reason with, but many use cases in modern web development is not possible in this setup and requires you to write your app as a long-running webserver process (e.g. websocket model).