private static function init()
 {
     if (!self::$initDone) {
         global $mysqlConfig;
         self::$mysqlConfigMaxPacketSize = $mysqlConfig['max_allowed_packet'];
         self::$mysqli = new mysqli($mysqlConfig['host'], $mysqlConfig['username'], $mysqlConfig['password'], $mysqlConfig['schema']);
         self::$mysqli->set_charset('utf8');
         self::$initDone = true;
         userManager::task_checkForExistingSession();
     }
 }