Description:
------------
Workaround:

$obj = $b->obj;
echo $obj::foo;

Test script:
---------------
<?php

class a{
   const foo = "test";
}
class b{
    public $obj = null;

    public function __construct(){
        $this->obj = new a;
    }
}

$b = new b;

echo $b->obj::foo; // Parse error!


Expected result:
----------------
test

Actual result:
--------------
Parse error: syntax error, unexpected '::' (T_PAAMAYIM_NEKUDOTAYIM)