Manual:$wgFileCacheDirectory

From MediaWiki.org

File Cache: $wgFileCacheDirectory
Directory where the cached page will be saved when using server-side caching.
Introduced in version:	pre 1.1.0
Removed in version:	still in use
Allowed Values:	absolute path
Default Value:	"{$wgUploadDirectory}/cache"

Other settings: Alphabetical | By Function

[edit] Details

This is the directory where cached page will be saved when using file caching.

If you switch on server-side file caching $wgUseFileCache = true;, then you can use this variable to specify where the cached pages will be saved on your server filesystem.

It's an absolute path, so you could specify somewhere under /tmp for example:

$wgFileCacheDirectory = "/tmp/yourcache";

...but you can specify relative to other directory path variables e.g.:

$wgFileCacheDirectory = "{$wgUploadDirectory}/cache"

This specifies a "cache" directory under the image uploads directory (normally called "images"). This is the default setting in fact.

You must create the directory and ensure it is writeable (by the php user). This is even true if you leave it as the default (You must create the "images/cache" directory).

See also File cache