public static function loadClass($className, $includeFile = null)
    {
        if (class_exists($className, false) || interface_exists($className, false)) {
            return true;
        }

        if (empty($includeFile)) {
            $includeFile = str_replace('_', DIRECTORY_SEPARATOR, $className) . '.php';
        }
        // Do not silence the errors with @, parse errors will not be seen
        include $includeFile;

        // Still no class?
        if (!class_exists($className, false) && !interface_exists($className, false)) {
            if (!self::fileExists($includeFile)) {
                throw new HTML_QuickForm2_NotFoundException(
                    "File '$includeFile' was not found"
                );
            } else {
                throw new HTML_QuickForm2_NotFoundException(
                    "Class '$className' was not found within file '$includeFile'"
                );
            }
        }
    }