public static function getConnection()
 {
     if (is_null(self::$dbConnection)) {
         $dbConnection = new mysqli(self::$mainDbLogin['server'], self::$mainDbLogin['user'], self::$mainDbLogin['passwd'], self::$mainDbLogin['db']);
         $dbConnection->set_charset('utf8');
         self::$mainDbLogin = null;
         self::$adminDbLogin = null;
         self::$dbConnection = $dbConnection;
     }
     return self::$dbConnection;
 }