public function update($id){
        $file_temp = $this->picture['tmp_name'];
        $user_file = $this->picture['name'];
        $timestamp = date("Y").date("m").date("d").date("h").date("i").date("s");
        $filepath = "uploads/".$timestamp.$user_file;
        if(move_uploaded_file($file_temp, $filepath)==false)
        {
            return false;
        }
        $db = new Db();

        $sql = "UPDATE product SET ProductName='$this->productName', CateID='$this->cateID', Price='$this->price', Quantity='$this->quantity', Description='$this->description', Picture='$filepath' WHERE
        ProductID=$id";

        $result = $db->query_execute($sql);
        return $result;
    }