public static function getConn(){
 
        try{
           if(self::$conn === null){
                self::$conn =  new self('mysql:host=' . DB_HOST . ';dbname=' . DB_NAME, DB_USER, DB_PASS);
                self::$conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
                self::$conn->exec('SET CHARACTER SET utf8');
            }
            return self::$conn;