CodeIgniter is already a very fast PHP framework, but that alone might not be fast enough for high traffic web applications. To get to the next level of performance you will need to implement some kind of caching.
Luckily for the CodeIgniter crowd, the framework comes with one of the fastest caching systems possible, Output Caching. Short of writing static HTML files or output caching to memory there is no faster way to serve pages.
However, if you have any degree of interactive or dynamic content, total output caching can be painful (if not impossible) to implement. Now there are other options, such as database caching and third party caching libraries, but none of them will be quite as fast as full output caching. So if at all possible that is what you should use.
Let me provide you with an overview of the caching systems available and a few of my tricks.
