Warning (2): substr() expects parameter 1 to be string, array given [CORE/src/Network/Http/Adapter/Stream.php, line 98]

What could be the reason for these errors http://i.imgur.com/oMwVBGS.png

My code is working properly on local server, after moving it to staging I got this error.

My code is as follow.

<?php

namespace App\Controller;

use Cake\Core\Configure;
use Cake\Network\Exception\NotFoundException;
use Cake\View\Exception\MissingTemplateException;
use Cake\ORM\TableRegistry;
use Cake\Network\Http\Client;
use Cake\Cache\Cache;

class WebController extends AppController
{

    public $helpers = ['Common'];

    public function home()
    {
        $http             = new Client();
        $apiBaseURL       = Configure::read('API_BASE_URL');
        $storeId          = Configure::read('API_STORE_ID');

        // Read areas list
        $areas = Cache::read('areas_list');
        if( empty($areas) ) {
            // Load from API and store in cache
            $response = $http->get($apiBaseURL.'areas', [
                'store_id' => $storeId,
            ]);

            $json = $response->json;

            if( isset($json['status']) && $json['status'] == 'success' ) {
                Cache::write('areas_list', $json['data']);
            }

            $areas = $json['data'];
            unset($json);
        }

        $this->set('areas', $areas);
    }

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