magento autologin

gistfile1.txt

// => if you know the customer id  
$customer = Mage::getModel('customer/customer')->load($id);
// => if you know the customer email address
$customer = Mage::getModel('customer/customer')->loadByEmail('[email protected]');
 
if($customer->getId())
{
   Mage::getSingleton('customer/session')->setCustomerAsLoggedIn($customer);
}