Description:
------------
Even though \ResourceBundle provides array access, it does not implement the 
\ArrayAccess interface nor allows to call isset() on its entries.

The following resource is necessary for the below test script:

en.txt:
---------------
en{
    Exists{"value"}
}

You need to convert this file to a .res file and place it in the same directory 
as the test script:

> genrb en.txt

Test script:
---------------
<?php

$bundle = new \ResourceBundle('en', __DIR__);

var_dump($bundle instanceof \ArrayAccess);
var_dump($bundle['Exists']);
var_dump($bundle['ExistsNot']);
var_dump(isset($bundle['ExistsNot']));


Expected result:
----------------
bool(true)
string(5) "value"
NULL
bool(false)

Actual result:
--------------
bool(false)
string(5) "value"
NULL

Fatal error: Cannot use object of type ResourceBundle as array in test.php on 
line 8

Call Stack:
    0.0002     128452   1. {main}() test.php:0