I made a module to calculate the price, based on given dimensions. This is working very nice, but when I login as user, the cart price resets to zero.

How do I solve this?

/// edit #1

After some digging, I found out that the vars: $quantity and $dimensionsPrice not working on quote merging. Do you know why? $dimensionPrice is from the custom attribute dimension_price.

/// edit #2

Turns out that when I want to add a product to the cart I have to use $product->getQty(). And when I login (so it merges), I have to use $quote_item->getQty(). Bit strange, but I fixed it with:

  $quantity = ($product->getQty()) ? $product->getQty() : $quote_item->getQty();

Now, I still not getting my attribute 'dimension price'...?


<?xml version="1.0"?>


class Roywulms_Dimensioncalculator_Model_Observer {
    public function __construct()

    public function changingPrice(Varien_Event_Observer $observer){

        $event = $observer->getEvent();
        $quote_item = $event->getQuoteItem();
        $product = $quote_item->getProduct();
        $quantity = $product->getQty();
        $options = $this->getProductOptions($quote_item);

        if(sizeof($options) > 0)
            foreach($options as $option)
                if($option['option_type'] == 'height')
                    $heightVal =  $option['value'];
                if($option['option_type'] == 'width')
                    $widthVal =  $option['value'];
            $basePrice = $product->getPrice();
            $dimensionsPrice =  $product->getDimensionPrice();

            if(isset($heightVal) && isset($widthVal)){
              $meter = $basePrice + ($widthVal * $heightVal)*$dimensionsPrice;
              $new_price = $meter*$quantity;

      function getProductOptions(&$item)
          $options = array();

          if ($optionIds = $item->getOptionByCode('option_ids')) {
              $options = array();
              foreach (explode(',', $optionIds->getValue()) as $optionId) {
                  if ($option = $item->getProduct()->getOptionById($optionId)) {

                      $quoteItemOption = $item->getOptionByCode('option_' . $option->getId());

                      $group = $option->groupFactory($option->getType())

                      $options[] = array(
                          'label' => $option->getTitle(),
                          'value' => $group->getFormattedOptionValue($quoteItemOption->getValue()),
                          'print_value' => $group->getPrintableOptionValue($quoteItemOption->getValue()),
                          'price'=> $group->getOptionPrice($quoteItemOption->getValue(),0),
                          'option_id' => $option->getId(),
                          'option_type' => $option->getType(),
                          'custom_view' => $group->isCustomizedView()
          if ($addOptions = $item->getOptionByCode('additional_options')) {
              $options = array_merge($options, unserialize($addOptions->getValue()));
          return $options;

Found the solution. Not the best I think, so if you know a better approach, please tell me.

Turns out I had two problems:

1: Quantity was not loaded on quote merge (happens when a user is logging in)


 $quantity = $product->getQty();


$quantity = ($product->getQty()) ? $product->getQty() : $quote_item->getQty();

2: Attribute was not loaded on quote merge.


$dimensionsPrice =  $product->getDimensionPrice();


$dimensionsPrice =  Mage::getModel('catalog/product')->load($product->getId())->getData('dimension_price');

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