public static function getContentType() {
    if(null === self::$contentType) {
      self::$contentType = @trim($_SERVER['HTTP_CONTENT_TYPE']);
      if(!self::$contentType) {
        self::$contentType = @trim($_SERVER['CONTENT_TYPE']);
        if(!self::$contentType) {
          self::$contentType = false;
        }
      }
    }
    return self::$contentType;
  }