PEAR_Downloader::configSet PHP Method

    function configSet($key, $value, $layer = 'user', $channel = false)
    {
        $this->config->set($key, $value, $layer, $channel);
        $this->_preferredState = $this->config->get('preferred_state', null, $channel);
        if (!$this->_preferredState) {
            // don't inadvertantly use a non-set preferred_state
            $this->_preferredState = null;
        }
    }