Description:
------------
Unexpected behavior in extended class, when using static variable in constructor and call the method directly

I was testing the concept of immutable classes and was coming to an point where i called the __construct method directly. I injected an static $var in the method and found that unexpected behavior. I seems that the C class that not defines an constructor once call the constructor with the previews incremented static var, but the direct call of the method gets an fresh static var. 
I think it is not normal to call the constructor directly as method, but when it is it should have same result as the class B. 
The call of  $c->__construct(); should get 6 not 1.

Or there any explanation to this?

Test script:
---------------
class A {
 public function __construct(){
     static $test  = 0;
     print (++$test);
 }
}
class B extends A {
    public function __construct(){
        parent::__construct();
    }
}
class C extends A {}

$a = new A;
$a->__construct();
$b = new B;
$b->__construct();
$c = new C;
$c->__construct();

Expected result:
----------------
123456

Actual result:
--------------
123451