Sometimes Magento can return unexpected errors after installing extensions or some code changes.

If you can no longer access to your site delete everything inside:

/var/cache

Just to give you brief introduction of APC Cache; Alternative PHP Cache (APC) is a free and open opcode cache which provides free, open, and robust framework for caching and optimizing PHP intermediate code. If you tweak APC well you can even cache application data (user cache).

Now, let me ask you this. Does your store despite all hard work still under performing? If the answer is yes then it’s a right time to induce Alternative PHP Cache (APC) to speed up your Magento store. Although, there are lots of opcode cache available like eaccelerator, Xcache etc.) still we are using APC just because of greater support and stability. APC cache is taken as default in PHP 6 so using APC makes more sense.

Symfony2 support several caching systems and one of them is APC cache.

This article is going to be short …. but, everything in Symfony2 is so developer friendly that do not require some huge knowledge to accomplish …

So, first of all what you should know: Apc cache is not going to work properly unless you are executing php scripts on linux server configuration either as apache user or FastCGI and the best way to be configured (from my personal experience is to run Php as with mod_fcgid, because running php as Apache user with often insufficient permissions could lead to other problems …).

But this article is not about how to configure your web server, but how easy is to configure Symfony2 project to use already working APC cache on server.

Improving Magento performance is at the top of the list for most professional Magento developers. There’s no doubt that enhancing the speed at which Magento performs can only be good for business.

One of the most important enhancements you can make to your Magento installation is to properly configure your MySQL database server.

A proper MySQL configuration requires a low level understanding of your underlying hardware and, primarily, the memory (RAM) available.

There is one specific MySQL configuration parameter above all others that will produce significant performance improvements and takes very little understanding to implement.