Beginner Q: How can I examine PHP variables after AJAX has altered them?

Specifically I am having an issue between stock levels and the UC Stock Notify module, however everything has been functioning perfectly fine for a few years now and works everywhere else except for one particular node's chosen product attribute, such as selecting the radio button for a Blue shirt.

Flowchart of the process:
- User clicks on the Radio button for a "Blue shirt"
- First UC Stock Notify jumps in to check the inventory level of the product selected.
-- If the stock level is greater than zero, then UC Stock Notify doesn't alter anything and the standard "Add to Cart" button appears.
-- If the stock level is zero or less than zero, then UC Stock Notify jumps in and alters the form by removing the "Add to Cart" button and inserting a new button that I've themed to read "Notify when back in stock".

Proper Behavior:
- Clicking a "Add to Cart" button uses AJAX (via the "Ubercart AJAX Cart" module) to seamlessly add the product to the user's cart and display a nice pop-up message that the product was added to their cart -- "Blue Shirt was added to your cart".
- Clicking a "Notify when back in stock" button reloads the page with a default message atop the page -- "Thank you for your interest in this product. We will notify you when it is available again" -- and a) adds their UID to a notification list for the specific product attribute configuration (ie. which radio button was selected), or b) provides a box for guests to enter their email to be notified when the product is back in stock.

What is happening instead:
I have a particular product attribute configured as in stock, ie Blue shirts are in stock. When the radio button to select the Blue shirt is clicked, the usual "Add to Cart" button appears. BUT, when the "Add to Cart" button is clicked, something very strange is happening:
- A nice pop-up message appears BUT the out-of-stock message of "Thank you for your interest in this product....." is somehow appearing in the pop-up instead of the "Blue shirt was added to your cart"
- Then the pop-up disappears and nothing else happens. The page does not reload, the user is not added to the product's notification list in the database, nothing is added to his or her shopping cart, just nothing happens.

It's exactly a combination of the two independent features: You get the nice pop-up as if we were adding the product to the cart but then you get the "Thank you for your interest..." message that isn't supposed to appear until the page reloads and the user has been added to a notification list.

I've experienced issues with stock where we accidentally have the same product number or SKU listed on two different nodes, where one node has the SKU configured as quantity "0" stock and the other as some positive number, which results in both nodes being able to add the product to the shopping cart despite one of them being out of stock. So I've searched the database a dozen times and have verified its not a SKU issue, I've even changed the SKU just to test this and so far no dice.

It is working perfectly fine on all other nodes that I have tested and in more than probably two years this is the first time I've ever had any issue with the UC Stock Notify module and I've not made any recent modifications that I can think of to cause this. It just seems so random I'm just about ready to delete the node and just copy everything over to a new node.

In the end here is what I am trying to trouble shoot so I can learn what is going on instead of ignoring it.

Here is the full function, but I don't think it's necessary to read it all so scroll down after this for a truncated version to save your time:

 /**
 * Implementation of hook_form_alter().
 */
function uc_stock_notify_form_alter(&$form, $form_state, $form_id) {
  if (user_access('subscribe to stock notices') && strstr($form_id, 'uc_product_add_to_cart_form_')) {
    // Special handling for uc_attributes, code taken directly from uc_attribute_cart_item().
    if (!empty($form_state['post']['attributes'])) {
      $combination = array();
      foreach ((array)$form_state['post']['attributes'] as $aid => $value) {
        if (is_numeric($value)) {
          $attribute = uc_attribute_load($aid, $form['nid']['#value'], 'product');
          if ($attribute && ($attribute->display == 1 || $attribute->display == 2)) {
            $combination[$aid] = $value;
          }
        }
      }
      ksort($combination);
      $result = db_result(db_query("SELECT model FROM {uc_product_adjustments} WHERE nid = %d AND combination LIKE '%s'", $form['nid']['#value'], serialize($combination)));
      $model = $result;
    }
    if (!$model) {
      $model = $form['node']['#value']->model;
    }

    if ($result = db_fetch_array(db_query("SELECT stock, threshold FROM {uc_product_stock} WHERE sku = '%s' AND active = 1", $model))) {
      // Use same rules as uc_multi_stock to decide if 0 or threshold level means "out of stock"
      $threshold = 0;
      if (module_exists('uc_multi_stock') && variable_get('uc_multi_stock_use_thershold', FALSE)) {
        $threshold = $result['threshold'];
      }

      if ($result['stock'] <= $threshold) {
        // product is out of stock
        unset($form['qty']);
        unset($form['submit']);
        $form['model'] = array('#type' => 'value', '#value' => $model);
        $form['notify'] = array(
          '#type' => 'submit',
          '#attributes' => array('class' => 'stock-notify'),
          '#value' => t('Notify when back in stock'),
        );
        unset($form['#validate']);
        $form['#submit'] = array('uc_stock_notify_form_submit');
      }
    }
  }
}

Here is a truncated version that I'm following in my mind to help me figure out what is happening:

 /**
 * Implementation of hook_form_alter().
 */
function uc_stock_notify_form_alter(&$form, $form_state, $form_id) {


// blah blah blah
// OK let's get the specific product attribute and store it's values in the array $model:

      $result = db_result(db_query("SELECT model FROM {uc_product_adjustments} WHERE nid = %d AND combination LIKE '%s'", $form['nid']['#value'], serialize($combination)));
      $model = $result;
    }

// OK If we found the model as an individual optional product attribute, then it's now set as $model.

    if (!$model) {
      $model = $form['node']['#value']->model;

// OK If $model wasn't set, then let's just set it as the original, default value of this node.

// OK Now let's even see if this product has any stock levels associated with it

    if ($result = db_fetch_array(db_query("SELECT stock, threshold FROM {uc_product_stock} WHERE sku = '%s' AND active = 1", $model))) {

// OK Great! We see it has some stock level associated with it

      $threshold = 0;
      if ($result['stock'] <= $threshold) {

// OK Product is obviously out of stock so let's modify the form by removing any 'Add to cart' features and insert the "Notify when back in stock" button

        unset($form['qty']);
        unset($form['submit']);
        $form['model'] = array('#type' => 'value', '#value' => $model);
        $form['notify'] = array(
          '#type' => 'submit',
          '#attributes' => array('class' => 'stock-notify'),
          '#value' => t('Notify when back in stock'),
        );
        unset($form['#validate']);

// And finally, the "Notify when back in stock" button:

        $form['#submit'] = array('uc_stock_notify_form_submit');

}

My Exact Request: I am trying to troubleshoot the $model PHP variable. This changes each time at the end-user when a different radio button is clicked.

I'd like to know if $model is indeed the exact specific product attribute of the exact SKU that I've entered as out of stock, or is $model for some reason not being updated and is only using the default variables ('red' and '10').

Here are the two functions in question:

      $result = db_result(db_query("SELECT model FROM {uc_product_adjustments} WHERE nid = %d AND combination LIKE '%s'", $form['nid']['#value'], serialize($combination)));
      $model = $result;

and

    if (!$model)
      $model = $form['node']['#value']->model;

My contention is that if the $result is coming up null, then just the default stuff from the node is being filled in for $model, which isn't gonna work when my node has multiple attributes - or product adjustments - in use.

Thoughts?

BigMike

Oh wow this looks very promising, thank you! I will check this out and report back-!

Mike