It's not possible to do in one line (just a constraint of PHP). I'd suggest adding a function that you can use, something like this:
public function getStaticVar($var) {
$class = new ReflectionClass($this->object);
$value = $class->getStaticPropertyValue($var);
return $value;
}
Using the Reflection library is the only way of dynamically accessing a dynamic static property in PHP.