Prado\Web\UI\ActiveControls\TStyleDiff::getCssClassDiff PHP Метод

    protected function getCssClassDiff()
    {
        if ($this->_old === null) {
            return $this->_new !== null && $this->_new->hasCssClass() ? $this->_new->getCssClass() : null;
        } else {
            return $this->_old->getCssClass() !== $this->_new->getCssClass() ? $this->_new->getCssClass() : null;
        }
    }