APC is Alternative PHP Cache. APC is an opcode cache that speed up your PHP applications, by caching both PHP code and user variables. Adding APC to an application improves application response time, reduces server load and make your users happy. This is a free, open, and robust framework for caching and optimizing PHP intermediate code. APC reads your PHP files, parses them into binary format and then caches them in memory so that each request for your PHP files and PHP library files can be served from the parsed cache.
You can see the difference by tracing your code through Xdebug or Zend debugger. You will definately notice a big difference.
Installing APC on RHEL:
First, login as Root User using “su” command.
If pecl doesn’t work, install php-devel
if still doesn’t work, if the pecl don’t work then, Please install PEAR first
Then create and add the following to apc.ini
Restart the Apache webserver:
Installing APC on Ubuntu:
$sudo /etc/init.d/apache2 restart
That’s it!!! You are done, APC is installed on your web server.