Description:
------------
By using FETCH_CLASS and __set overloading, __construct will be executed after populating object properties;

Reproduce code:
---------------
class Test
{
	protected $prop;
	function __construct()
	{
		$this->prop['a'] = null;
		$this->prop['b'] = null;
		$this->prop['c'] = null;
	}

	function __set($name, $value)
	{
		$this->prop[$name] = $value;
	}
}
$query = "SELECT 1 AS a, 2 AS b, 3 AS c";
$sth = $objPDO->prepare($query);
$sth->execute();
$result = $sth->fetchAll(PDO::FETCH_CLASS, 'Test');
var_dump($result);


Expected result:
----------------
I expect

 array(1) { [0]=> object(Test)#8 (1) { ["prop:protected"]=> array(3) {
   ["a"]=> string(1) "1" ["b"]=> string(1) "2" ["c"]=> string(1) "3" } } }

Actual result:
--------------
array(1) { [0]=> object(Test)#8 (1) { ["prop:protected"]=> array(3) {
   ["a"]=> NULL ["b"]=> NULL ["c"]=> NULL } } }

Try to comment __construct code and you'll obtain the right result.