This is the name of the directory where template caches are
       stored. By default this is
       ./cache, meaning that
       Smarty will look for the cache/ directory
        in the same directory  as the executing php script.
       This directory must
     be writeable by the web server,
     see install for more info.
     
     You can also use your own custom cache implementation
       to control cache files, which will ignore this setting.
       See also
       $use_sub_dirs.
      
This setting must be either a relative or absolute path. include_path is not used for writing files.
It is not recommended to put this directory under the web server document root.
        As of Smarty 3.1 the attribute $cache_dir is no longer accessible directly. Use 
        getCacheDir() and 
        setCacheDir() instead.
       
  See also
  getCacheDir(), 
  setCacheDir(),
  $caching,
  $use_sub_dirs,
  $cache_lifetime,
  $cache_modified_check
  and the
  caching section.