add product with special price to cart drupal7

Question

I used the following code to implement "add to cart" in my tpl.php file, and it works fine:

$product=commerce_product_load($node->field_product['und'][0]['product_id']);
$line_item = commerce_product_line_item_new($product,1);
$line_item->data['context']['product_ids'] = array($product->product_id);
$show_quantity = TRUE;

$form = drupal_get_form('commerce_cart_add_to_cart_form', $line_item,$show_quantity);
print render($form);

Right now, it can only use its original price. However, I want to add this product with a special price to the cart and use this special price to checkout.

I have already created a "Price" field named "field_special_price", and if I use print_r($product), I can see its value and can use the value by $product->field_special_price['und'][0]['amount']

Answer 1

You need to use a rule that acts on the "Calculating the sales price of an item" and then set the price using that rule. Here is an example: https://drupalcommerce.org/user-guide/sell-price-calculation

Answer 2

Thank you @nvahalik!

Based on @nvahalik answer, I create a new rule. I created a new field because I have so many different products and each product has its own special price. Here are the steps:

1. create a new price field named "field_special_price"
2. create a new pricing rule (event:Calculating the sell price of a product) (you can find the steps in the link from @nvahalik answer)

3. Add first condition : Entity has Field (the image is my first condition)

4. Add second condition: Entity has Field

Entity-Data selector: "commerce-line-item:commerce-product"(based on first condition)

Field-Value: "field_special_price"

5.Add third condition: Data value is empty

Data to check: commerce-line-item:commerce-product:field_special_price(based on second condition)

Select "Negate"

6. Add first action:Calculate a value

Hint: Mix "commerce-line-item:commerce-product:field_special_price:amount" & "commerce-line-item:commerce-product:commerce-price:amount"

7. Add second action: Set the unit price to a specific amount

Hint: Amount- Data selector: "(the variable name from first action)"