function connect()
 {
     include "db-conf.php";
     try {
         if (Db::$_db) {
             return Db::$_db;
         }
         $opt = [PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION, PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC];
         $db = new PDO('mysql:host=localhost;dbname=' . $dbConfig["dbname"], $dbConfig["user"], $dbConfig["password"], $opt);
         //TODO: move to config
         Db::$_db = $db;
         return $db;
     } catch (PDOException $e) {
         echo $e->getMessage();
     }
 }