related to #1693 changed smarty version to 4.1.0

include/smarty/docs/programmers/api-variables/variable-cache-dir.md

@@ -0,0 +1,35 @@
+\$cache\_dir {#variable.cache.dir}
+============
+
+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](#installing.smarty.basic) for more info.
+
+You can also use your own [custom cache implementation](#caching.custom)
+to control cache files, which will ignore this setting. See also
+[`$use_sub_dirs`](#variable.use.sub.dirs).
+
+> **Note**
+>
+> This setting must be either a relative or absolute path. include\_path
+> is not used for writing files.
+
+> **Note**
+>
+> It is not recommended to put this directory under the web server
+> document root.
+
+> **Note**
+>
+> As of Smarty 3.1 the attribute \$cache\_dir is no longer accessible
+> directly. Use [`getCacheDir()`](#api.get.cache.dir) and
+> [`setCacheDir()`](#api.set.cache.dir) instead.
+
+See also [`getCacheDir()`](#api.get.cache.dir),
+[`setCacheDir()`](#api.set.cache.dir), [`$caching`](#variable.caching),
+[`$use_sub_dirs`](#variable.use.sub.dirs),
+[`$cache_lifetime`](#variable.cache.lifetime),
+[`$cache_modified_check`](#variable.cache.modified.check) and the
+[caching section](#caching).