CI_Encrypt::get_key PHP Method

    public function get_key($key = '')
    {
        if ($key === '') {
            if ($this->encryption_key !== '') {
                return $this->encryption_key;
            }
            $key = config_item('encryption_key');
            if (!strlen($key)) {
                show_error('In order to use the encryption class requires that you set an encryption key in your config file.');
            }
        }
        return md5($key);
    }