<?php
class Marketplace extends Curl
{
    public function getOffers()
    {
        $this->get('/marketplace/offers');

        return $this->getResponseBody();
    }
}

<?php
class Marketplace
{
    private $_curl;

    public function __construct(Curl $curl)
    {
        $this->_curl = $curl;
    }

    public function getOffers()
    {
        $this->_curl->get('/marketplace/offers');

        return $this->_curl->getResponseBody();
    }
}