How to solve zend array config merge

Module.php

<?php
/**
 * @author: Maksim Norkin
 * @email: maksim.norkin@ruptela.lt
 */

namespace ZR\Cache\Adapter\Redis;

use Zend\Config\Reader\Json;
use Zend\EventManager\EventInterface;
use Zend\ModuleManager\ModuleEvent;
use Zend\ModuleManager\ModuleManager;
use Zend\Mvc\ModuleRouteListener;
use Zend\Mvc\MvcEvent;

/**
 * Class Module
 *
 * @package ZR\Cache\Adapter\Redis
 */
class Module
{
    /**
     * @param EventInterface|MvcEvent $e
     */
    public function onBootstrap(EventInterface $e)
    {
        $eventManager = $e->getApplication()->getEventManager();
        $moduleRouteListener = new ModuleRouteListener();
        $moduleRouteListener->attach($eventManager);
    }

    public function init(ModuleManager $moduleManager)
    {
        $events = $moduleManager->getEventManager();

        // Registering a listener at default priority, 1, which will trigger
        // after the ConfigListener merges config.
        $events->attach(ModuleEvent::EVENT_MERGE_CONFIG, array($this, 'onMergeConfig'));
    }

    /**
     * @param ModuleEvent $e
     */
    public function onMergeConfig(ModuleEvent $e)
    {
        $configListener = $e->getConfigListener();
        $config = $configListener->getMergedConfig(false);
        $localConfig = $this->getConfig();
        $adapterName = key($localConfig['zr-cache']['adapter']['redis']);

        $systemAdapterConnectionCollection = $config['zr-cache']['adapter']['redis'][$adapterName]['connections'];
        $localAdapterConnectionCollection = $localConfig['zr-cache']['adapter']['redis'][$adapterName]['connections'];

        $mergedAdapterConnectionCollection = new \ArrayIterator(\Functional\filter(
            $systemAdapterConnectionCollection,
            function($systemAdapterConnection) use ($localAdapterConnectionCollection) {
                return !\Functional\contains($localAdapterConnectionCollection, $systemAdapterConnection);
            }
        ));

        $config['zr-cache']['adapter']['redis'][$adapterName]['connections'] =
            $mergedAdapterConnectionCollection->getArrayCopy();

        $configListener->setMergedConfig($config);
    }

    /**
     * @return array
     */
    public function getConfig()
    {
        /** @var Json $reader */
        $reader = new Json();
        return $reader->fromFile(__DIR__ . '/config/module.config.json');
    }

    /**
     * @return array
     */
    public function getAutoloaderConfig()
    {
        return array(
            'Zend\Loader\StandardAutoloader' => array(
                'namespaces' => array(
                    __NAMESPACE__ => __DIR__ . '/src/' . __NAMESPACE__,
                ),
            ),
        );
    }

}