I mean... Let's that we just make an AJAX request and inser the result inside a div#result..
In the backend the script use ob_flush() to send the header but not terminate the request until it's terminated (with exit or ob_flush_end)
The content will be loaded into the #result only when the request terminate (exit or ob_flush_end) or it'll be loaded every time the script send the header by ob_flush?
Update:
I'll use jQuery load() to make the request & PHP to answer it
Yes, content will be returned, but the XHR object's readyState will not be set to 4, so if you are relying on that to update your div (which most JS libraries' AJAX auto updaters do), you won't see it automatically.
来源：https://stackoverflow.com/questions/2164330/if-you-flush-the-content-ob-flush-of-an-ajax-request-the-content-will-get-loa