I have a magento site that I have been working on.

So recently I decided to install new update to a 1.9.1 version in magento however I disocvered later that the extensions I also want to download are not compatible with the newest version.

So I decided to delete the extension files I updated and upload the old extensions again within app/var/package

However this caused great error and now the frontend and admin of my website won't load.

I have an error log within my public\_html and there is an error that display:

```
PHP Fatal error: class 'Mage_Admin_Helper_Data' not found in /home/company/public_html/app/code/core/Mage/Core/Controller/Varien/Router/Admin.php on line 123

```

The line within:

```
  public function collectRoutes($configArea, $useRouterName)
{
    if ((string)Mage::getConfig()->getNode(Mage_Adminhtml_Helper_Data::XML_PATH_USE_CUSTOM_ADMIN_PATH)) {
        $customUrl = (string)Mage::getConfig()->getNode(Mage_Adminhtml_Helper_Data::XML_PATH_CUSTOM_ADMIN_PATH);
        $xmlPath = Mage_Adminhtml_Helper_Data::XML_PATH_ADMINHTML_ROUTER_FRONTNAME;
        if ((string)Mage::getConfig()->getNode($xmlPath) != $customUrl) {
            Mage::getConfig()->setNode($xmlPath, $customUrl, true);
        }
    }
    parent::collectRoutes($configArea, $useRouterName);
}

```

The line 123 being:

```
if ((string)Mage::getConfig()->getNode($xmlPath) != $customUrl) {

```

Help will be must appreciated.