jpcache is a lightweight, full page caching system for PHP, thus reducing server-load, as pages are generated less often. It dramatically speeds up the serving of your pages, by caching the ouput of pages and returning them instead of compiling the php-page.
Turck MMCache is a PHP Accelerator & Encoder. It increases performance of PHP scripts by caching them in compiled state, so that the overhead of compiling is almost completely eliminated. Also it uses some optimizations for speed up of scripts execution.
The ionCube PHP Accelerator is an easily installed PHP Zend engine extension that provides a PHP cache, and is capable of delivering a substantial acceleration of PHP scripts without requiring any script changes, loss of dynamic content, or other application compromises.