Mage registry key “_singleton/core/resource” already exists in magento

Question

I am facing this problem on my site Mage registry key \"_singleton/core/resource\" already exists, Please help me how to solve this error.

I have checked the folder and

Answer 1

In index.php put this directly after require_once $mageFilename;

$app = Mage::app();
$cache = $app->getCache();
$cache->clean();

Refresh your broken web page, then remove the code.