The Alternative PHP Cache (APC) is a free and open opcode cache for PHP. Its goal is to provide a free, open, and robust framework for caching and optimizing PHP intermediate code. And you can boost your php web application using this modules. For example you can use it in WordPress using W3 Total Cache.
To install Alternative PHP Cache (APC) you can use PECL (repository for PHP Extensions):
1. Open your ssh with root access.
2. Install APC dependency pcre prior install APC:
yum install pcre-devel #For Centos aptitude install libpcre3-dev #For Ubuntu/Debian
3. Install APC:
pecl install apc
4. Wait until it is finished.
5. Test it by make a file in your web directory using phpinfo()
<?php phpinfo(); ?>
Now you can use APC for better cache mechanism, see PHP APC book at php.net.
For WordPress blog you can use W3 Total Cache to use PHP APC.