Description:
------------
I use json_encode() with a depth (usually 1) to trim complex objects in some test cases in order to do comparisons.
But it returns false now if the object being encoded contains a member which is an object.
I have to set the depth to 2 but it means it doesn't trim like what I did before.

But I'm not sure if this bug is related to PHP 5.6.26. It might have been introduced in earlier versions.

Test script:
---------------
class Person
{
    public $name;
    public $age;
    public $role;
}

class Role
{
    public $name;
}

$person = new Person();
$person->name = 'Name';
$person->age = 20;
$person->role = new Role();
$jsonObj = json_encode($person, 0, 1);
// $jsonObj === false

Expected result:
----------------
{"name":"Name","age":20,"role":null}

Actual result:
--------------
false