[PHP-DOC] &$this?

[Ming-Chieh Lee]

does anyone know what does &$this mean?  I saw this on the php.net tuturial
for references inside a constructor.
I thought that $this is already a reference?
The way it was used :
class Foo
{
    function Foo($name)
    {
        // create a reference inside the global array $globalref
        global $globalref;
        $globalref[] = &$this;
        // set name to passed value
        $this->setName($name);
        // and put it out
        $this->echoName();
    }
thanks for any input!