By default PHP scripts are compiled on each access. This will become a real performance killer once your website hits a certain load. There is a number of Opcode caches available which try to overcome this recompiling issue by storing precompiled versions of your scripts in a cache. This blog entry will explain how to integrate the Alternative PHP Cache (APC) into your PHP5 installation. This tutorial is based on a Debian installation, but it should also work with alternative distributions.

APC ist installed using the PHP Extension Community Library (PECL). Using PECL ist similar to using the PEAR Library. Before you can install APC via PECL, make sure that you have the following packages installed:

aptitude install php5-dev php5-gd

Downloading compiling and installation of APC using PECL ist a breeze. Just run from the command line:

pecl install APC

Now all you need to do is to add the following line to your php.ini file which you should find in /etc/php5/apache2/:

extension=apc.so

Once you restart Apache, caching will be enabled with default settings of APC. By default APC will use 30 MB memory to cache your PHP files. It is a good idea to tailor this setting to your server. This can be done with the following line in php.ini:

apc.shm_size=30