Since you already know how to create timer functions and classes, in this tutorial, I'll create some concrete examples that show where these timing mechanisms can be applied in order to evaluate the performance of certain PHP applications.

They create a few classes that connect to a database and pull out rows (handing it off to a Result class). They use these classes in two examples - one with compression (output buffering) and one without using their Timer class to evaluate the differences.

The groundwork is laid first, giving a simple "Hello world" example to show how the code flows. They show how the buffering system works and how to use a callback function to modify the contents of the buffer before outputting (including a full replace function to text within the buffer from an array). They follow that with a look at creating your own HTML tags and using the gzip compression functionality to speed up your pages.