Json listener for Buzz http client

JsonListener.php

<?php

use Buzz\Listener\ListenerInterface;
use Buzz\Message\MessageInterface;
use Buzz\Message\RequestInterface;

class JsonListener implements ListenerInterface
{
    /**
     * {@inheritdoc}
     */
    public function preSend(RequestInterface $request)
    {
        $request->addHeader('Accept: application/json');
        $request->setContent(json_encode($request->getContent()));
    }

    /**
     * {@inheritdoc}
     */
    public function postSend(RequestInterface $request, MessageInterface $response)
    {
        $content = json_decode($response->getContent(), true);

        if (JSON_ERROR_NONE !== json_last_error()) {
            throw new \RuntimeException('Invalid JSON.');
        }

        $response->setContent(is_array($content) ? $content : array());
    }
}