Output Buffer Control means less bandwidth, fewer database queries, faster pages.
One really neat feature of PHP is the ability to control the output to the browser while the script is running. We will cover using output buffers to store your page in a buffer as the PHP script runs, then when done, have it gzipped and sent out in one neat and tiny package. Also we will cover
template caching which can be used to give dynamic sites the speed of a static html site.
This is easy code to add to a website and the gains can be great.
Here are the deets on PHP.net and Tim's profile.