Where is price of product added to cart, or should that be How is it?

[strelitzia]

I'm currently working on a module and i need to be able to change the product price as it is added to cart.
For example, Product A price is $25, but it is also available for $5 dollars if certain conditions are met.

I've got the product to show the correct price in an ajax popup that allows it to be added to cart, but when it goes to cart, it charges the full price.
Both prices are stored in the db, one as products_price, the other as products_price_offer.
The new pages i have built all reference products_price_offer as i want, but i just can't get it to pass the offer price to the shopping cart.

I think if i can find where it builds the array for adding to cart i can manipulate this to use the offer price instead, but i just can't seem to find it.

Any help would be appreciated because i seem to be getting nowhere fast now.

Thanks

[strelitzia]

Seems no one can offer any help so far.

I've looked further into this and am even more confused by it now.
tpl_product_info_display uses this to get the product price for display:

echo $one_time . ((zen_has_product_attributes_values((int)$_GET['products_id']) and $flag_show_product_info_starting_at == 1) ? TEXT_BASE_PRICE : '') . zen_get_products_display_price((int)$_GET['products_id']);

So i looked at functions_prices.php for function zen_get_products_display_price($products_id) {
I then hard coded a value into $display_normal_price for testing purposes.

Refresh the product page and the coded price showed correctly.
Except, when added to cart, it used the price from the database, and not the one i hard coded.

This suggest to me that the process of adding to cart does not take the variables used to output the product page, and it can't be using zen_get_products_display_price.

So what does it use? Where does it get the price that is used for the cart?

[lhungil]

...
For example, Product A price is $25, but it is also available for $5 dollars if certain conditions are met.
...

Can you give us an example condition?
Does the "Better Together" plugin fit your needs? Or "group discounts"? (these would be be good examples to look at for pricing changes).

[strelitzia]

I looked at those and didn't really find anything that pointed me in the right direction.

I can't believe it's so difficult to add a product to cart referencing the database for products_price_offer instead of products_price when conditions are met.

Dr Byte, if you could give me some info on how zc processes prices i would appreciate it.

[strelitzia]

From what i can see, it doesn't actually carry an array full of ALL the product data over to the shopping cart, but instead uses $prid to hold the product id, plus some other checks that are made for attributes etc. The details in the cart are then pulled in from the database in includes/classes/shopping_cart.php.
If i'm right on this, that explains why i can't get the cart to display the correct price, even though the product page does.

So what i'm thinking is that if i set a var when the product is added to cart via the ajax system, which is only used for offers, i should be able to store that var with the product id in TABLE_CUSTOMERS_BASKET if they are logged in, or in the session contents if not, and depending upon the value of the var, change the code around line 1083 in shopping_cart.php to reference the alternative price. I'll also need to do the same where it calculates the total etc i suspect, but not looked that far yet.

Anyone got any better suggestions, or comments on whether or not this is the best way forward (Aimed at ZC team as they know the core better than anyone else.)

[DrByte]

From what i can see, it doesn't actually carry an array full of ALL the product data over to the shopping cart, but instead uses $prid to hold the product id, plus some other checks that are made for attributes etc. The details in the cart are then pulled in from the database in includes/classes/shopping_cart.php.
If i'm right on this, that explains why i can't get the cart to display the correct price, even though the product page does.

Correct. That's the behavior that was inherited from osC. It will be changed for v2, but for now that's how it works.
And then that information is passed to the order class during checkout. Both the shopping cart and order class pull the actual price from the database in real time ... not based on any price modifications passed via the URL. To pass modifications via the URL (or your ajax thing or whatever) you'll need to pass a get or post value which you then use to modify the price in those two classes. In some cases you can use custom observer classes to do that, if the necessary notifier hooks exist.

[strelitzia]

Dr Byte,
Thanks for the confirmation on this. At least i know my detective work was correct and that i was looking in the right direction.

[strelitzia]

To pass modifications via the URL (or your ajax thing or whatever) you'll need to pass a get or post value which you then use to modify the price in those two classes.

I changed this:

$the_button = PRODUCTS_ORDER_QTY_TEXT . '<input type="text" name="cart_quantity" value="' . (zen_get_buy_now_qty($_GET['products_id'])) . '" maxlength="6" size="4" /><br />' . zen_get_products_quantity_min_units_display((int)$_GET['products_id']) . '<br />' . zen_draw_hidden_field('products_id', (int)$_GET['products_id']) . zen_image_submit(BUTTON_IMAGE_IN_CART, BUTTON_IN_CART_ALT);

to this:

$the_button = PRODUCTS_ORDER_QTY_TEXT . '<input type="text" name="cart_quantity" value="' . (zen_get_buy_now_qty($_GET['products_id'])) . '" maxlength="6" size="4" /><br />' . zen_get_products_quantity_min_units_display((int)$_GET['products_id']) . '<br />' . zen_draw_hidden_field('products_id', (int)$_GET['products_id']) . zen_draw_hidden_field('g_ad', (int)$_GET['1']) . zen_image_submit(BUTTON_IMAGE_IN_CART, BUTTON_IN_CART_ALT);

in tpl_product_info_display.php

I then went to includes/classes/shopping_cart.php and replaced the relevant instances of

$products_price = $products->fields['products_price'];

with

if($_POST['g_ad'] == '1') {
$products_price = $products->fields['products_price_offer'];
}else{
$products_price = $products->fields['products_price'];
}

but i still get the normal price displaying in the cart.

I assume $_POST['g_ad'] isn't showing as '1'

Any suggestions where i'm going wrong? Do i need to do anything else with g_ad to get it to work?

Thanks
Steve