Annoying PHP warning - Cannot modify header information

All of sudden I got below error -

"Warning: Cannot modify header information - headers already sent by (output started at XXXXXX.php:23) in XXXXXX.php on line 143"

WTH!

Then searched online and found out that you should not have white spaces or blank lines before "?php", and after "?". Did that, still got the same error.

Do more researching..., and found out this - In the PHP.ini file, you need to turn on the buffer.
"output_buffering = On"

After I updated the this PHP.ini file, this annoying error is finally gone now.