public static function scan($xml, DOMDocument $dom = null)
    {
        // If running with PHP-FPM we perform an heuristic scan
        // We cannot use libxml_disable_entity_loader because of this bug
        // @see https://bugs.php.net/bug.php?id=64938
        if (self::isPhpFpm()) {
            self::heuristicScan($xml);
        }

        if (null === $dom) {
            $simpleXml = true;
            $dom = new DOMDocument();
        }

        if (!self::isPhpFpm()) {
            $loadEntities = libxml_disable_entity_loader(true);
            $useInternalXmlErrors = libxml_use_internal_errors(true);
        }

        // Load XML with network access disabled (LIBXML_NONET)
        // error disabled with @ for PHP-FPM scenario
        set_error_handler(array('fproject\common\utils\XmlSecurity', 'loadXmlErrorHandler'), E_WARNING);

        $result = $dom->loadXML($xml, LIBXML_NONET);
        restore_error_handler();

        if (!$result) {
            // Entity load to previous setting
            if (!self::isPhpFpm()) {
                libxml_disable_entity_loader($loadEntities);
                libxml_use_internal_errors($useInternalXmlErrors);
            }
            return false;
        }

        // Scan for potential XEE attacks using ENTITY, if not PHP-FPM
        if (!self::isPhpFpm()) {
            foreach ($dom->childNodes as $child) {
                if ($child->nodeType === XML_DOCUMENT_TYPE_NODE) {
                    if ($child->entities->length > 0) {
                        throw new Exception(self::ENTITY_DETECT);
                    }
                }
            }
        }

        // Entity load to previous setting
        if (!self::isPhpFpm()) {
            libxml_disable_entity_loader($loadEntities);
            libxml_use_internal_errors($useInternalXmlErrors);
        }

        if (isset($simpleXml)) {
            $result = simplexml_import_dom($dom);
            if (!$result instanceof SimpleXMLElement) {
                return false;
            }
            return $result;
        }
        return $dom;
    }