private function _map_posted_data()
 {
     $product = new Product();
     $product->set_name($_POST['name']);
     $product->set_description($_POST['description']);
     $product->set_sell_price($_POST['sell_price']);
     $product->set_cost_price($_POST['cost_price']);
     $product->set_photo($_POST['photo']);
     $product->set_status($_POST['status']);
     return $product;
 }
 public function get_by_id($id)
 {
     $this->db->connect();
     $sql = "SELECT id,name,description,sell_price,cost_price,photo,status from tbl_products WHERE id=?";
     $stmt = $this->db->initStatement($sql);
     $stmt->bind_param("i", $id);
     $stmt->execute();
     $stmt->bind_result($id, $name, $description, $sell_price, $cost_price, $photo, $status);
     while ($stmt->fetch()) {
         $product = new Product();
         $product->set_id($id);
         $product->set_name($name);
         $product->set_description($description);
         $product->set_sell_price($sell_price);
         $product->set_cost_price($cost_price);
         $product->set_photo($photo);
         $product->set_status($status);
     }
     $this->db->close();
     return $product;
 }