Fatal error: Class 'Mage' not found

Question

I updated Magento to the latest version via Magento connect , it was success but after the update I get blank screen for admin and frontend.

When I put

if (isset($_SERVER['MAGE_IS_DEVELOPER_MODE']) || true) {
  Mage::setIsDeveloperMode(true);
}

at my index.php

I get below error:

Fatal error: Class 'Mage' not found in how can i solve it please help i want urgent fix .

Answer 1

Make sure the file app/Mage.php exists and that you have this in your index.php file

define('MAGENTO_ROOT', getcwd());
....
require_once $mageFilename;
....