Description:
------------
When a closure returns an anonymous class that implements an interface is returned in a file that is require()d multiple times, subsequent return values have the interface information stripped.

I discovered this behavior while writing unit tests around a configuration tool (asserting that the returned value implemented an interface) - the test would pass if it was the _first_ test to run, but fail otherwise. It would also pass if I ran the tests with process isolation enabled. The attached script is the simplest reproduce case I could come up with.

Test script:
---------------
// run.php
<?php
interface I {}
require 'data.php'; // comment this line out to get the expected behavior
$data = require 'data.php';
print_r(class_implements($data['I']()));

// data.php
<?php
return [
  'I' => function() {
    return new class implements I {};
  },
];

Expected result:
----------------
$ php run.php
Array
(
    [I] => I
)


Actual result:
--------------
$ php run.php
Array
(
)