On ibzi's blog today, there's a quick guide to introducing caching to your PHP application via a simple PHP file to create the cached pages.
Caching your pages can be pretty useful, especially if you have PHP-generated pages that uses a lot of MySQL queries. Once your pages are cached, your server won't waste speed and RAM on regenerating the pages, it will just load it from the cache. I'm going to show you how to get PHP to cache your pages, and you can probably do this within 5 minutes.
You'll need to be able to add (and use) an .htaccess file for Apache to use this method, but once it's set up, the simple script works like a charm. It prepends the caching functionality to each page and checks to see if a copy already exists. If it does, it displays it and if not, it will display it and create the cached file.
But this is only true in a few number of cases. If script execution is based on cookies, other websites (web services), timeouts, running processes or some other external factors it will unable to determine if the page is already created or not, because the request URI and the post data is not decisive what page content is to be generated. Especially when using clean URLs (e.g. when you work with the Zend framework) this will be the situation.