Laravel 5.1: Class that implements a base PHP interface errors out

I've been working on modifying/converting the Recurly PHP client library to work in Laravel 5.1.

I got namespacing to work to the point that I can reference the Recurly library classes appropriately, but have run into the wall of interfaces that those classes implement causing the classes to fail out.

As a note: these interfaces are base php interfaces, but I can't figure out how to get Laravel 5.1 to let a class implement a base php interface that isn't a 'baked-in' Laravel interface.

System PHP version: 5.6.22

Example Class declaration causing issues:

<?php

namespace App\Libraries\Recurly;

class Recurly_CurrencyList implements ArrayAccess, Countable, IteratorAggregate
{

This is the error message that gets thrown:

Interface 'App\Libraries\Recurly\ArrayAccess' not found

via Chebli Mohamed