Some doubts about output_buffering

I have some questions about output_buffering on the Internet.
I saw this file on the Internet.
Http://www.cnblogs.com/zemliu/archive/2012/05/11/2495293.html

As mentioned above
PHP output sequence

1. open the php output cache: echo, print-> php output_buffring-> server buffering-> browser display

2. php output cache not enabled: echo, print-> server buffering-> browser display

Is this true ?????


And
Ob_flush () function: extracts data from PHP buffering and places the data in server buffering.
Flush () function: extract the data of Server buffering and put it into browser buffering.

So when we want to force the buffer zone output, write ob_flush () first and write flush ()
Is that true?
------ Solution --------------------
Yes.

However, for ob_flush () and flush (), it depends on the control requirements.
Echo 'A ';
Ob_flush ();
Flush ();
Sleep (1 );
And
Echo 'A ';
Flush ();
Ob_flush ();
Sleep (1 );
The difference is that the former will immediately see a, while the latter will wait a second to see