APC, or Alternative PHP Cache, is a PHP module that caches the output code of database-driven script apps. Dynamic PHP sites keep their content within a database that is accessed whenever a visitor loads a webpage. The content which should be viewed is gathered and the code is parsed and compiled before it is delivered to the website visitor. All of these actions take some processing time and include reading and writing on the web server for every single page that is opened. While this cannot be avoided for websites with constantly changing content material, there are many websites that have the exact same content on many of their pages all the time - blogs, info portals, hotel and restaurant Internet sites, etcetera. APC is very useful for such sites because it caches the previously compiled code and shows it any time visitors browse the cached pages, so the code doesn't have to be parsed and compiled all over again. This will not only decrease the server load, but it'll also increase the speed of any site a few times.