Programmatically logging in customer doesn't work

Question

I'm using this code to login a customer programmatically:

<?php
require_once ("app/Mage.php");    

Mage::app('default');

// Init a Magento session. This is super ultra important
Mage::getSingleton('core/session', array('name' => 'frontend'));

// $customer Mage_Customer_Model_Customer
// We get an instance of the customer model for the actual website
$customer = Mage::getModel('customer/customer')
    ->setWebsiteId(Mage::app()->getStore()->getWebsiteId());

// Load the client with the appropriate email
$email = "[email protected]";
$customer->loadByEmail($email);

// Get a customer session
$session = Mage::getSingleton('customer/session');

// Login an check the customer by his database userId
if ($session->loginById($customer->getId())) {
    echo '<div>Succesfull loginById</div>';
} else {
    echo '<div>Error in loginById</div>';
}

if ($session->isLoggedIn()) {
    echo '<div>Welcome</div>';
} else {
    echo '<div>Denied</div>';
}

But it's not working, the result I'm getting in the browser is:

Succesfull loginById

Denied

What could be the issue here?

---

EDIT

Some new information: I've tried this script on a different shop we have running and it works perfectly there. Why would it work on one but not the other?

---

EDIT 2

More troubleshooting has resulted in the conclusion that $session->getId() returns NULL while it should return an actual ID. Still no idea why this shop doesn't return a session id while the other one does.

Answer 1

You're looking for

Mage::getSingleton('customer/session')->setCustomerAsLoggedIn($customer);

Where $customer is a loaded instance of Mage_Customer_Model_Customer

Answer 2

<?php
require_once ("app/Mage.php");
umask(0);

$websiteId = 1;
Mage::run('store_view_code', 'store');
Mage::init($websiteId, 'website');

$email = '[email protected]';

$customer = Mage::getModel('customer/customer');
$customer->setWebsiteId($websiteId);
$customer->loadByEmail($email);
$session = Mage::getSingleton('customer/session');

if ($customer->getId()) {
    $session->setCustomerAsLoggedIn($customer);

    $url = 'http://www.domain.com/test';
    $session->setAfterAuthUrl($url);
    header('Location: ' . $session->getAfterAuthUrl());
    exit();
}