Error: Fatal error: Call to a member function addProduct() on a non-object in xxx/src/class.AdminService.php on line 130






public function addProduct($product_id, $categorie, $product_name, $description, $manufacturer, $price)
    {
        $returnValue = null;

         
this is line 130:   --->        $returnValue = $this->m_dao->addProduct($product_id, $categorie, $product_name, $description, $manufacturer, $price);


        return $returnValue;
    }