Can I use Panels context keywords in PHP functions? I'm using the privatemsg module and I would like to display the number of unread messages a user has on his/her profile page.  I attempted to use %user, which is the context keyword for the user currently being viewed.

According to the privatemsg API documentation, the function for this is privatemsg_unread_count().  I tried calling the function like this:

privatemsg_unread_count("%user");

But I get an error: Notice: Trying to get property of non-object in privatemsg_unread_count()

The function takes an account argument, which as far as I can tell (I'm not very skilled in PHP) is an array that stores the values for a given user.  Am I going the wrong way with trying to use the context keywords?
Just call the function without any argument and it will return the unread message count for the current user.