Oscommerce Add products to cart manually

In order to add products manually by Id or customize cart manually in OSCommerce

we need to first include the following file

require("includes/application_top.php")

What  this does is automatically includes the following class

require(DIR_WS_CLASSES . 'shopping_cart.php');(line 126)

and instantiates an object of class

if (!tep_session_is_registered('cart') || !is_object($cart)) {

    tep_session_register('cart');

    $cart = new shoppingCart; 

} 

or you can yourself include these files and create an object

But for any action in oscommerce I prefer to include application_top.php

If you are building up a new cart add

$cart->reset();

This will reset your cart which is only required if you are planning to add a new cart in my case I was sending all Items from another website to my oscommerce website so I decided to reset cart first

Now let us suppose we have item information in an array $items

foreach($items as $item)

{

       $attributes = isset($HTTP_POST_VARS['id']) ? $HTTP_POST_VARS['id'] : '';
       $cart->add_cart($item['id'],$item['quant'],$attributes);
      //In case cart is not empty and you want to add quantity to an item
      $cart->add_cart($item['id'], $cart->get_quantity('$item['id']')+1);
}

Then add the following lines

//Cleans any product with quantity zero
$cart->cleanup();

//Calculates the weight and total cost in all finalizes your cart

$cart->calculate();

That's All