Manual:WebStart.php/ja

これはウェブリクエストの初期のセットアップを行います, it should be called by all web access points (including index.php). ある程度のセキュリティの確認をし、プロファイラをスタートさせ、verify that LocalSettings.php exists and prints an error if not.

It includes LocalSettings.php, starts the output buffer and includes Setup.php if the  constant is not defined.