致命错误：对function.php中的非对象调用成员函数add_to_cart（）

我正在定制woo commerce插件，将产品从前端添加到购物车中。我已经在functions.php中编写了这个函数，但是我遇到了一个致命错误。有人知道怎么解决吗

  if (isset($_POST["addcustomcarts"]))
            {
           echo $_SERVER[QUERY_STRING];
          // echo $_SERVER[REQUEST_URI];
            echo "i am in if";
            //exit();
        add_filter('woocommerce_before_cart', 'customcart');

        function customcart() { 
           echo "i am in function";

        //global $woocommerce;

        $my_post = array(
          'post_title'    => 'My post',
          'post_content'  => 'This is my post.',
          'post_status'   => 'publish',
          'post_author'   => 1,
          'post_type'     =>'product'

        );


        // Insert the post into the database
         $product_ID=wp_insert_post( $my_post );

         add_post_meta($product_ID, '_regular_price', 100, $unique);
         add_post_meta($product_ID, '_price', 100, $unique);
          add_post_meta($product_ID, '_stock_status', 'instock', $unique);


          //Getting error on this line.
          $woocommerce->cart->add_to_cart( $product_ID, $quantity=1 );




         exit( wp_redirect( home_url( "cart" ) ) );
        }

        customcart();
          }

---

获取此错误-->致命错误：在C:\wamp\www\cutting-edge\u server\wordpress\u theme\wp content\themes\cutting\age\responsive\functions.php的第56行对非对象调用成员函数add\u to\u cart（），为什么要注释这一行 //全球商业？我认为这可能是问题所在