As I was in the process of moving this site into Git and having a local version, I have been trying to move as many paths as possible into the config.php. One of them included the cache path for image sizer. Since the local and production paths are different, I wanted some way for them to be dynamic. In my config.php file, I am using $_SERVER['DOCUMENT_ROOT'] to set the base_path. I could have enabled PHP in the template and then use the $_SERVER['DOCUMENT_ROOT'], but that seemed like a silly reason to enable PHP.
So I made a plugin that gives you access to everything in the $config array without having to use PHP.
To see all possible values, just pass in “all”: