Probably a stupid question but I’ll ask anyway – stop php request from client?

I’m trying to get my head around how php processes request (via apache).

If I call a php page which on the server side calls a database to insert some data and then returns the data back to the client.

What happens if you call the page but then immediately stop the request on the client, will the whole php script run until completion or will it stop when the client stops the request? And if so what happens to the output of the php script if the request is stopped?