RestClient无法得到响应

i'm newbie in PHP. I use restclient (https://github.com/tcdent/php-restclient) to request as below:

<?php

require 'restclient.php';

        $api = new RestClient();
        $result = $api->get("https://api.github.com/repos/phatls/CallCenter_Customer/issues?state=all");
        if($result->info->http_code == 200)
            echo ($result->response);
        else 
            echo "false";

?>

It works greatly. But with:

<?php

        require 'restclient.php';
        $api = new RestClient();
        $result = $api->get("http://beka.vn/api/BkMobileLogin/GetGroup/phat.ls");
        if($result->info->http_code == 200)
             echo ($result->response);
         else 
            echo "false";

?>

It returns false. Please help me if you don't have any inconvenient. thanks

please read official page documentation.link

Or follow this official example

$api = new RestClient([
'base_url' => "http://vimeo.com/api/v2", 
'format' => "php"
]);
$result = $api->get("tcdent/info");
if($result->info->http_code == 200)
         echo ($result->response);
     else 
        echo "false";