Fun thing about that : core PHP used to and still is very very close to HTTP, to the point where I would say your average decent PHP programmer used to knows more about how HTTP work that your average other similar language where the web library abstract stuff. Eg a PHP dev knows a form has to be multipart/form-data if you send files etc ...

But one of the if not THE major exception is this : buffering and flushing works automagically and a lot of PHP dev end up massively blindsinded by it at some point

PS: with the rise of modern PHP and it's high quality object based framework, this become less and less true

PS2: I am not in ANY way saying anything good or bad or superior or inferior about any dev here, just a difference in approach