I've found the harder way that using 'pecl install apc' is not a good way on my Debian system. The reason is that as soon as I update my apache or php packages, the apc is not up to date with the rest of the system and can cause a lot of headache as it did for me.

On a Debian system in production the best way is to maintain a clean apt install by installing apc the following way:

apt-get install php-apc

This way all the dependencies will be taken care of on the next package update and the consistency is much better.