AC full page cache: Capture and cache the output of whole page scripts

This class can capture and cache the output of whole page scripts.

It can check if the current page script cache file exists and is up to date. If it is, it outputs the contents of the cache file.

Otherwise it starts capturing the script output and registers a PHP shutdown function that will retrieve the captured output and stores it in the cache file when the script exits.

What is the best PHP cache whole page class?
Cache the whole Web page