Description:
------------
When I use json_encode on a class, this get the properties values directly and bypass the __get magic method.

It would be great if I could control the properties with __get

Test script:
---------------
class Example {

    public foo;

    public function __construct() {
        $this->foo = 'bar;
    }

    public function __get($param) {
        return $this->$param . ' modified';
    }

}

$foo = new Example();
echo json_encode($foo);

Expected result:
----------------
{"foo":"bar modified"}

Actual result:
--------------
{"foo":"bar"}