ho provato a cambiare in

function isAuthenticated()
{
$USER= $_SERVER['PHP_AUTH_USER']; //;global'PHP_AUTH_USER'
$PW= $_SERVER['PHP_AUTH_PW']; //;global

if ($this->authenticated < 0)
{
if(isset($USER))
{
$this->authenticated = $this->validate($USER, $PW);
}
else
{
$this->authenticated = 0;
echo "user ".$USER." ::";
}
}

return $this->authenticated;
}

nulla...