Why do we need an APC PHP cache? Because PHP source files are not compiled as in Java, C, C++ etc. Therefore would take a certain amount of time to compile the source file before launching the application. To reduce the time that is spent compiling the source code every time a request is made, developers use the APC PHP Cache.
Some company’s sell this program as a plug in for PHP, while there are many open source PHP cache options available as well. There are many variations of this plug-in available and some of them optimize the code and then caching and some just caching. APC which stands for Alternative PHP Cache is still in active development and also open source and free. APC is available at PHP.net and is available in source code form. Therefore developers will have to compile it before installing. This is not a difficult process for many Linux based platforms and information is freely available on the internet.
Once you’ve installed APC you will notice that there is a huge improvement in performance and response times for your website. If you have many websites running on your server, you can filter which ones need to use cache. This is to reduce the amount of memory used for caching. The apc.filters property allows you to specify which websites need caching and which don’t.