Создайте файл и попробуйте его
require_once "app/Mage.php";
umask(0);
Mage::app();
// require_once $_SERVER['DOCUMENT_ROOT'] . "/mage1/app/Mage.php";
// Customer Information
$firstname = "krishana";
$lastname = "singh";
$email = "krish.bhati@gmail.com";
$password = "myverysecretpassword";
// Website and Store details
$websiteId = Mage::app()->getWebsite()->getId();
$store = Mage::app()->getStore();
$customer = Mage::getModel("customer/customer");
$customer->website_id = $websiteId;
$customer->setStore($store);
$mageRunCode = isset ( $_SERVER ['MAGE_RUN_CODE'] ) ? $_SERVER ['MAGE_RUN_CODE'] : '';
$mageRunType = isset ( $_SERVER ['MAGE_RUN_TYPE'] ) ? $_SERVER ['MAGE_RUN_TYPE'] : 'store';
$app = Mage::app ( $mageRunCode, $mageRunType );
Mage::getSingleton('core/session', array('name' => 'frontend'));
$session = Mage::getSingleton('customer/session');
$session->start();
$customer->loadByEmail($email);
$customer_id= $customer->getId();
if($customer_id){
Mage_Core_Model_Session_Abstract_Varien::start();
$session->login($email, $password);
$session->setCustomerAsLoggedIn($session->getCustomer());
echo $session->isLoggedIn() ? $session->getCustomer()->getName().' is online!' : 'not logged in';
}