Manual:$wgForeignFileRepos

Details
Properties required for all repos:
 * class
 * The class name for the repository. May come from the core or an extension. The core repository classes are LocalRepo, ForeignDBRepo, FSRepo and ForeignAPIRepo.


 * name
 * A unique name for the repository.

For all core repos:
 * url
 * Base public URL


 * hashLevels
 * The number of directory levels for hash-based division of files


 * thumbScriptUrl
 * The URL for thumb.php (optional, not recommended)


 * transformVia404
 * Whether to skip media file transformation on parse and rely on a 404 handler instead.


 * initialCapital
 * Equivalent to $wgCapitalLinks, determines whether file names implicitly start with a capital letter. The current implementation may give incorrect description page links when the local $wgCapitalLinks and initialCapital are mismatched.


 * pathDisclosureProtection
 * May be 'paranoid' to remove all parameters from error messages, 'none' to leave the paths in unchanged, or 'simple' to replace paths with place holders. Default for LocalRepo is 'simple'.


 * descBaseUrl
 * URL of image description pages, e.g. http://en.wikipedia.org/wiki/Image:


 * scriptDirUrl
 * URL of the MediaWiki installation, equivalent to $wgScriptPath, e.g. http://en.wikipedia.org/w


 * articleUrl
 * Equivalent to $wgArticlePath, e.g. http://en.wikipedia.org/wiki/$1


 * fetchDescription
 * Fetch the text of the remote file description page. Equivalent to $wgFetchCommonsDescriptions.


 * descriptionCacheExpiry
 * If set to 0, no caching will be used. Set to 1 or more (seconds) to define how long the local cache of description pages will last. Must set fetchDescription to true to use.

ForeignAPIRepo class:
 * apibase
 * The base URL for the remote repository's API (eg: http://commons.wikimedia.org/w/api.php). Only used for ForeignAPIRepo.


 * apiThumbCacheExpiry
 * How long to cache thumbs locally for. Not setting this or setting to 0 disables local thumb caching


 * apiThumbCacheDir
 * Where to put the locally cached thumbs. Will be a sub-folder of your $wgUploadPath.


 * Note: In order for local thumb caching to work, both of the above settings (apiThumbCacheExpiry and apiThumbCacheDir) must be set. Failure to set one or the other will prevent local caching of thumbnails.

ForeignDBRepo class:
 * dbType, dbServer, dbUser, dbPassword, dbName, dbFlags
 * equivalent to the corresponding member of $wgDBservers


 * tablePrefix
 * Table prefix, the foreign wiki's $wgDBprefix


 * hasSharedCache
 * True if the wiki's shared cache is accessible via the local $wgMemc

Default Value (code in Setup.php) :

Using files from Wikimedia Commons : ForeignAPIRepo
You can set your wiki to use media from Wikimedia Commons directly (if you have MediaWiki 1.13 or later and PHP >= 5.2.0). However, please beware any legal implications, and keep in mind that you are hotlinking images from another site. If you have a lot of visitors, please consider a solution that allows images to be cached on your own servers. Also see InstantCommons for some considerations about this.

The below code enabled media files from Wikimedia Commons on your site:

Using files from a local folder : FSRepo
You can set your wiki to use media from a single folder. This is just a demonstration feature at present, and will probably be too slow for busy wikis or slow servers due to the lack of caching.

The below code enabled media files from it: