Api.php

<?php

namespace Payum\Skeleton;

use Http\Message\MessageFactory;
use Payum\Core\Exception\Http\HttpException;
use Payum\Core\Exception\InvalidArgumentException;
use Payum\Core\HttpClientInterface;

class Api
{
    /**
     * @var HttpClientInterface
     */
    protected $client;

    /**
     * @var MessageFactory
     */
    protected $messageFactory;

    /**
     * @var array
     */
    protected $options = [];

    /**
     * @throws InvalidArgumentException if an option is invalid
     */
    public function __construct(array $options, HttpClientInterface $client, MessageFactory $messageFactory)
    {
        $this->options = $options;
        $this->client = $client;
        $this->messageFactory = $messageFactory;
    }

    /**
     * @return array
     */
    protected function doRequest($method, array $fields)
    {
        $headers = [];

        $request = $this->messageFactory->createRequest($method, $this->getApiEndpoint(), $headers, http_build_query($fields));

        $response = $this->client->send($request);

        if (! ($response->getStatusCode() >= 200 && $response->getStatusCode() < 300)) {
            throw HttpException::factory($request, $response);
        }

        return $response;
    }

    /**
     * @return string
     */
    protected function getApiEndpoint()
    {
        return $this->options['sandbox'] ? 'http://sandbox.example.com' : 'http://example.com';
    }
}