public function render($smiley, $isXhtml = true) {
        if (!$this->hasSmiley($smiley)) {
            return null;
        }

        $path = sprintf('%s%s.%s',
            $this->getConfig('path'),
            $this->_smilies[$smiley],
            $this->getConfig('extension'));

        if ($isXhtml) {
            $tpl = '<img class="decoda-emoticon" src="%s" alt="" />';
        } else {
            $tpl = '<img class="decoda-emoticon" src="%s" alt="">';
        }

        return sprintf($tpl, $path);
    }