VersionPress\Storages\Serialization\IniSerializer::preserveNULLs PHP Method

    private static function preserveNULLs($iniString)
    {
        https:
        //regex101.com/r/tF2wK2/1
        $re = "/= (<null>)\\r?\\n/m";
        return preg_replace_callback($re, function ($m) {
            return str_replace('= ', '= ' . self::$nullMarker, $m[0]);
        }, $iniString);
    }