PHP 5.5 compatibility issue

[Yuriy Abramov]

> php -v
PHP 5.5.9-1ubuntu4.20 (cli) (built: Oct  3 2016 13:00:37) 

> cat 1.php 
<?php

require_once __DIR__.'/vendor/autoload.php';

$statusCake = new StatusCake\Client('***', '***');
var_dump( $statusCake->validAccount() );

> php 1.php 
PHP Fatal error:  Cannot access private property StatusCake\Client::$url in .../vendor/happydemon/statuscake/src/StatusCake/Call.php on line 33