function replaceEntities($string, $replaceEntities = XML_UTIL_ENTITIES_XML,
        $encoding = 'ISO-8859-1')
    {
        switch ($replaceEntities) {
        case XML_UTIL_ENTITIES_XML:
            return strtr($string, array(
                '&'  => '&amp;',
                '>'  => '&gt;',
                '<'  => '&lt;',
                '"'  => '&quot;',
                '\'' => '&apos;' ));
            break;
        case XML_UTIL_ENTITIES_XML_REQUIRED:
            return strtr($string, array(
                '&' => '&amp;',
                '<' => '&lt;',
                '"' => '&quot;' ));
            break;
        case XML_UTIL_ENTITIES_HTML:
            return htmlentities($string, ENT_COMPAT, $encoding);
            break;
        }
        return $string;
    }