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. So what does this mean for Drupal?
An opcode cache is used to keep compiled PHP code in memory. In a nutshell, when there's a request for a Drupal node, there are all kinds of PHP code that need to be compiled before PHP can execute that code to query the database, create the webpage, and send it to the browser. The more complex your Drupal site, IE the more modules you have installed, the more PHP code that needs to be compiled. This compilation process occurs on every request to your Drupal site. By installing and enabling an opcode cache, your server will compile all the PHP code once, then store it in memory for later use. When a request happens again for the same PHP code, the opcode …
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