$rootDir = Mage::getRoot(); echo $rootDir; // outputs something like '/home/user/public_html'
require_once(Mage::getRoot() . '/app/Mage.php');In this example, we are using `Mage::getRoot()` to include the Magento core file by concatenating the root directory with the path to the `Mage.php` file. This method is part of the Magento Core Package Library.