accessing product pages with products_model and products_id

I have found this old thread http://www.zen-cart.com/forum/showthread.php?t=66448

and it is exactly what I want to do but unfortunately the link that gives the information on which file to put the code in is broken...
where would the code snippet from that thread be placed in order for it to work?

if (!isset($_GET['products_id']) && isset($_GET['products_model'])) {
    $_GET['products_model'] = zen_db_prepare_input($_GET['products_model']);
    $get_products_id = $db->Execute("SELECT products_id FROM " . TABLE_PRODUCTS . " WHERE products_model='" . zen_db_input($_GET['products_model']) . "' LIMIT 1");
    if($get_products_id->EOF)
      $_GET['products_id'] = 0;
    else
      $_GET['products_id'] = $get_products_id->fields['products_id'];
  }

thanks,
Will

I'd try the top of

includes/modules/pages/product_info/header_php.php

just below the notifier.

that was it!!...thank you very much!

Hi,

I am trying to be abel to add items to my cart by either using product_id or products_model. I am think I could write some code so that when it receives a model number i could run a query that would grab the corresponding id number.

where would i need to put this code? also any help with the coce would be appreciated.

for example:
this is what the it does now

<form name="multiple_products_cart_quantity" action="http://websitehere/index.php?     main_page=index&cPath=4_55_59&sort=20a&action=multiple_products_add_product" method="post" enctype="multipart/form-data">

I want it to look like this..

thanks,
Will

i want to know where i can edit the code that does:

<input type="text" name="products_id[6114]" value="0" size="4">

it is what creates the input for the quantity in the product listing page

/includes/modules/your_custom_template_name/product_listing.php