private static function makeSureLogFileExists()
 {
     if (self::$logFilePath == null) {
         $folder = __DIR__ . DIRECTORY_SEPARATOR . "log";
         if (!file_exists($folder)) {
             mkdir($folder);
         }
         self::$logFilePath = $folder . DIRECTORY_SEPARATOR . basename(__FILE__, ".php") . "_" . self::formTs() . ".log";
         touch(self::$logFilePath);
     }
 }