What does the PHP operator =& mean?

Possible Duplicate: What do the "=&" and "&=" operators in PHP mean?

I found the operator "=&" in the following code, and I do not know what it means. What does it mean and what does it do?

The code where I read it:

function ContentParseRoute($segments)
{
    $vars = array();

    //Get the active menu item
    $menu =& JSite::getMenu();
    $item =& $menu->getActive();

    // Count route segments
    $count = count($segments);
        ....