Manual:$IP/ja

Manually setting this variable to the absolute path to MediaWiki on disk from was necessary in older versions of MediaWiki. However, at least since MediaWiki 1.18, manually defining  in LocalSettings.php is no longer needed and no longer works as you may expect. It will default to the current working directory and it can be used without the need to define it manually.

If you have to override the default value you have to declare the environment variable. See the documentation of your webserver for how to do it.

詳細
IP は Include Path を表します. この変数はウィキのインストール先のベースであるローカル ファイル パスを保持します. 既定値を上書きするいかなる理由がある場合でも、完全なファイル パスを使用していることを確認してください. パスの末尾にスラッシュを含めないでください.

In MediaWiki 1.16 and prior, where the DefaultSettings.php file still had to be loaded from inside LocalSettings.php, the directory to load it from was determined by the IP variable.

他の変数とは異なり、既定値は DefaultSettings.php ではなく WebStart.php で設定されています.

Setting the  environmental variable can sometimes be useful when running maintenance scripts that are in non-standard directories. (Maintenance scripts by default use the parent of the current working directory as $IP).