Magento 1.9.x: How to add an extra fee to order while adding item to cart programmatically?

Question

I also asked here https://magento.stackexchange.com/questions/167982/magento-1-9-x-how-to-add-an-extra-fee-to-order-while-adding-item-to-cart-progra but didn't get any answer yet so I am asking here.

I am adding item programmatically into cart (code below) and want to add an extra fee to order. I found a lot of results here also but unable to follow as I am new in magento. Can anyone please share where to create file (observer, config.xml etc with path) and what should be the name of the file? Below code is adding item to cart successfully but I am unable to add fee to complete order.

Any help will be really appreciable.

Thanks in advance. My code is:

$productId = 13114;
$price_extra = 50.00;
$product_model = Mage::getModel('catalog/product');
$code = Mage::app()->getStore()->getCode();
$_product = Mage::getModel('catalog/product')->load($productId);
$_product->setMinimalPrice($price_extra);

$cart = Mage::getSingleton('checkout/cart');
$cart->init();
$params = array(
    'product' => $productId,
    'related_product' => null,
    'qty' => 1,
    'options' => array(
        2 => array('7', '8', '9', '10', '11', '12'),
        1 => array('1', '2', '3', '4', '5', '6'),
    )
);
$customer = Mage::getSingleton('customer/session')->getCustomer();
$storeId = $customer->getStoreId();

$cart->addProduct($_product, $params);
$cart->save();
Mage::getSingleton('checkout/session')->setCartWasUpdated(true);

Answer 1

After you load your product you can set price of that product, Replace your this line

$_product->setMinimalPrice($price_extra);

with this

$_product->setPrice($_product->getPrice()+$price_extra);

Answer 2

You need to set custom price using event observer

Use this event. sales_quote_add_item 1. config.xml

<frontend>
    <events>
        <sales_quote_add_item>
            <observers>
                <mymodule_observer>
                    <type>singleton</type>
                    <class>MyCompany_MyModule_Model_Observer</class>
                    <method>updateCartPrice</method>
                </mymodule_observer>
            </observers>
        </sales_quote_add_item>
    </events>
</frontend>

2. Observer.php

class MyCompany_Mymodule_Model_Observer {

public function updateCartPrice(Varien_Event_Observer $observer) {
    $event = $observer->getEvent();
    $quoteItem = $event->getQuoteItem();
    $product = $item->getProduct();

    $extraPrice = 100;
    $customPrice = $product->getFinalPrice() + $extraPrice;
    $quoteItem->setOriginalCustomPrice($customPrice);
    $quoteItem->setCustomPrice($customPrice);
    $quoteItem->save();
}

}

Try this. It will work for you.