$cache_dir 缓存目录变量

This is the name of the directory where template caches are stored. By default this is "./cache", meaning that it will look for the cache directory in the same directory as the executing php script. You can also use your own custom cache handler function to control cache files, which will ignore this setting.
这是存放模板缓存的目录名.默认情况下,它是:"./cache",也就是说你可以在和php执行脚本相同目录下寻找缓存目录.你也可以用你自己的自定义缓存处理函数来控制缓存文件,它将会忽略这项设置.

Technical Note: This setting must be either a relative or absolute path. include_path is not used for writing files.
技巧:这项设置必须是一个相对或绝对路径.包含路径不用于写文件.

Technical Note: It is not recommended to put this directory under the web server document root.
技巧:不推荐将此目录放在web服务器根目录下.