public function isInstalled($installPath)
    {
        $manifest = Util::getPackageManifest($installPath);

        if ($manifest === false) {
            return false;
        }

        $xml = simplexml_load_file($manifest);

        if($xml instanceof \SimpleXMLElement)
        {
            $type    = (string) $xml->attributes()->type;
            $element = Util::getNameFromManifest($installPath);

            if (empty($element)) {
                return false;
            }

            $extension = $this->getExtension($element, $type);

            if (!is_object($extension)) {
                return false;
            }

            return isset($extension->id) && $extension->id > 0;
        }
        
        return false;
    }