I don't see code blocks on this page: http://symfony.com/doc/2.7/cookbook/session/sessions_directory.html

I tried all the versions by using the switcher, and used Firefox and Chromium, I never saw the code.

Example of the output:

This means that when you clear the cache, any current sessions will also be deleted:

Using a different directory to save session data is one method to ensure that your current sessions aren't lost when you clear Symfony's cache.

Here is the corresponding page in this repository: https://github.com/symfony/symfony-docs/blob/2.7/cookbook/session/sessions_directory.rst