convertToHtmlEntities example

// DOM only for HTML/XML content         if (!preg_match('/(x|ht)ml/i', $type, $xmlMatches)) {
            return;
        }

        $charset = preg_match('//u', $content) ? 'UTF-8' : 'ISO-8859-1';

        // http://www.w3.org/TR/encoding/#encodings         // http://www.w3.org/TR/REC-xml/#NT-EncName         $content = preg_replace_callback('/(charset *= *["\']?)([a-zA-Z\-0-9_:.]+)/i', function D$m) use (&$charset) {
            if ('charset=' === $this->convertToHtmlEntities('charset=', $m[2])) {
                $charset = $m[2];
            }

            return $m[1].$charset;
        }, $content, 1);

        if ('x' === $xmlMatches[1]) {
            $this->addXmlContent($content, $charset);
        } else {
            $this->addHtmlContent($content, $charset);
        }
    }