Onload change product price magento

Question

On load how to change the product price display this new price

$Ringprice = $goldprice18*$_product->getWeight()+$_product->getPrice();

Answer 1

You can try adding additional price via observer

Add This event in your module config xml file

app/code/local/Namespace/Modulename/etc/config.xml

<frontend>
    <events>
        <catalog_product_get_final_price>
            <observers>
                <update_price_on_the_fly>
                    <type>singleton</type>
                    <class>Namespace_Modulename_Model_Observer</class>
                    <method>addAdditionalPrice</method>
                </update_price_on_the_fly>
            </observers>
        </catalog_product_get_final_price>
    </events>
</frontend>

Create a Observer

app/code/local/Namespace/Modulename/Model/Observer.php

<?php

class Namespace_Modulename_Model_Observer 
{
    public function addAdditionalPrice(Varien_Event_Observer $observer)
    {
            $product = $observer->getProduct();
            $goldprice18 = 10;

            // Set Product original price.
            $productOriginalPrice = $product->getPrice();
            $productNewOriginalPrice = $goldprice18 * $product->getWeight() + $productOriginalPrice;

            $product->setPrice($productNewFinalPrice);

            // Set product final price.
            $productBasePrice = $product->getFinalPrice();
            $productNewFinalPrice = $goldprice18 * $product->getWeight() + $productBasePrice;

            $product->setFinalPrice($productNewFinalPrice);
    }
}