First, read ob_gzhandler
Geez, I really have to list everything when talking to you eh? ob_gzhandler SUCKS. You can't even set the compression level. I've never used it because of that. Not worth mentioning.
Second, you don't need to use the output buffer for anything, if you programme your application correctly. Zlib or no Zlib
Almost right - everything except the use of ob_* functions, these are not necessary.
Of course you don't NEED to use them to employ output buffering, I already said so much.
The latter doesn't make use of the OB. It is still buffering, but it is much more efficient than use php's Output Buffer.
I challenge that statement. Proof please.
If you're not using content compression, output buffering is very unlikely to affect the speed of your web server by any great amount - if anything, it should help it serve pages /faster/ because of the optimised data sending. Content compression does take up a little CPU time on both the server and on clients visiting your site, but it's pretty small. On the up-side, content compression should decrease the amount of bandwidth you use by 40-60%, which means your server will spend less time sending data across the network. The compression level you achieve depends entirely on the kind of content you serve up - if you have lots of pictures, which content compression won't affect, your compression level will be lower; if you're sending lots of XML, which is a naturally repeating format that is very easy to compress, your compression level will be much higher. It's important to remember that only the output of your PHP script will be compressed - images, CSS files, etc, are all served as normal.
Hmmm.. faster eh? Ok, it's not exactly an exact measure, and it doesn't compare to buffer using variables, but it is something.
Use output buffering (See ob_start). This will speed up your PHP code by 5-15% if you frequently print or echo in your code.
Ok, now were talking. We have numbers.
It can easily be seen that output buffering is around twice as efficient over concatenation to a single string in the PHP world.
Wait... What happend? Concatenation (with .=) is about twice as slow as output buffering? Imagine that. He even has a diagram. Then it must be true! LOL...