A bridge Diggin_Http_Charset & Guzzle4. enable auto convert charset encoding to UTF-8.
php composer.phar require sasezaki/diggin-guzzle4-charset-subscriber
<?php
use GuzzleHttp\Client;
use DigginGuzzle4CharsetSubscriber\CharsetSubscriber;
require_once __DIR__.'./vendor/autoload.php';
$url = 'http://d.hatena.ne.jp/'; // euc-jp web-site
$client = new Client();
$client->getEmitter()->attach(new CharsetSubscriber);
$res = $client->get($url);
var_dump(strip_tags($res->getBody()->__toString())); // will be output as UTF-8
If you looking for Guzzle3.