Mage::getSingleton('admin/session')->getUser() is returning null

Question

I have a custom module in my magento (version 1.5) and it's meant to load the currently logged in admin username like this in one of my controller:

$current_user = Mage::getSingleton('admin/session')->getUser();
if ($current_user) {
    $this->current_user = $current_user->getUsername();
} else {
    $this->current_user = '';
}

When the code runs, $this->current_user is empty, so I did a var_dump($current_user); exit(); and it appears to be null akways (even if I am logged in).

Any ideas why this might be?

Answer 1

Based on the comments...
Magento does not share the admin and frontend sessions. even if you are logged in in the backend in one tab and you use the frontend on a different tab in the same browsers, the sessions are separated. Frontend does not know about the admin session and the admin session does not know about the frontend session.
So what you are trying to achieve is not really possible.
There are workarounds, but I would not recommend them.
fronend and backend should stay separate for security reasons.
But here you go:
This should work if you you store the sessions in the db: http://www.stackoverflow.com/a/16034942/2047249

Answer 2

Mage::getSingleton('core/session', array('name'=>'adminhtml'));
//verify if the user is logged in to the backend
if(Mage::getSingleton('admin/session')->isLoggedIn()){
  echo "Admin Logged in";
}
else
{
  echo "You need to be logged in as an admin.";
}