Let’s discover how to add custom fields in the last step of the WooCommerce order process : the checkout page. We will also see how to modify the cart price according to the value of these fields.

Information

This is a translation of a tutorial I published on my French blog (Personnaliser l’expérience du tunnel de commande WooCommerce).

During the development of a custom e-commerce store, third-party extensions are often used to customize the customer’s shopping experience.

But depending on the need, it is sometimes difficult to find a shoe that fits.

Let’s take some time here to understand how it is possible to customize the WooCommerce Checkout page to get a unique tunnel. With the right tools in hand, we will realize that it may not be that complicated!

How to add custom extra fields on the WooCommerce checkout form page?

Information

The complete code of this tutorial has been grouped in a WordPress plugin freely downloadable here.

Objective of the tutorial

Before detailing what we are going to put in place, there’ s nothing like a picture to illustrate…

We are creating an online shop for buyers in a hurry. On the order page, we will add a field — before the billing details — where the customer will be able to:

  • check a checkbox to indicate that he is in a hurry 🏃‍♂️
  • use a drop-down menu to choose the emergency level 🚨

Depending on the urgency of his request, an additional fee will be added to his cart. This extra charge is equivalent to:

  • 2 times the value of the cart for an ultra-fast shipment within the hour
  • 1.5 times for shipment within 6 hours
  • 1.25 times for shipment within 12 hours
  • 1.1 times for a shipment before the next day

This little exercise will then allow us to add new fields on the WooCommerce checkout page, to validate these fields during the purchase and to add possible charges to the cart according to the value of these fields.

Once the order is placed, we will save the values of our 2 fields (by default totally unknown to WooCommerce) in the order metadata.

Handcrafting a new WooCommerce checkout experience

How to add custom fields to the checkout billing form?

The first step will be to add the new fields that we want to appear in the checkout form.

PHP

We’ll take advantage of woocommerce_checkout_billing hook to inject new fields in the order form. This hook will allow us to display them before the billing details requested to the customer.

Good to know

Look at the /templates/checkout/form-checkout.php template in WooCommerce to discover the different hooks available to insert your own additional fields. As I’m writing, WooCommerce offers no less than 8 actions placed at various places in the form. You should find what you need to place your new fields wherever you want!

Here, nothing fancy: we add our own HTML code to make new fields appear (in our case, a checkbox and a drop-down menu).

Warning

Be sure to use unique name attributes on your fields to avoid conflicts with any other native/third-party fields.

At the end of the function, a JavaScript code will tell WooCommerce to “restart its shopping cart price calculation” each time an interaction has been made on one of our two fields. We will be able to keep a cart price always up to date according to the urgency choice chosen by the buyer.

Triggering the update_checkout event on the body of the page allows WooCommerce to understand that some information has been modified and that it’s time to re-calculate the cart to deliver an adequate price to the customer.

Validate these checkout custom fields

Our fields are created, their values are sent to WooCommerce when we send the order. However, it’s a good idea to add a validation layer and check the validity of our new fields to potentially prevent the order from being sent and display an error message.

PHP

It’s the woocommerce_checkout_process hook in WooCommerce that allows us to perform any logic necessary to consider an order request as valid or invalid.

In our case, we are going to:

  • lines 4 to 7: make sure the drop-down menu for the emergency level has a value other than the default “Please select…” option.
  • lines 9 to 11: check that the emergency level sent corresponds to a valid emergency level among our 4 known ones. In this way, it is forbidden to send an unknown value.

In its validation process, WooCommerce will focus on error notices. If no notice is present, it will consider the order parameters as valid and will be able to continue its work (creating the order, sending e-mails, redirecting the user on the thank you page, etc.).

You can therefore invalidate the order request by adding an error notice with wc_add_notice( $message, 'error' ). The message will be displayed at the top of the page for the user to correct their error(s).

Dynamically modify the cart price according to these fields

As described in the introduction, we want to apply an additional charge to the cart according to the degree of urgency chosen by the buyer. It is the woocommerce_cart_calculate_fees hook that will allow us to dynamically apply charges on the cart.

PHP

After a few preliminary checks (lines 2 to 16), we will calculate the price of the fee to be applied. We use WC()->cart->add_fee() to add a fee charge to the shopping cart by indicating its name as the first parameter and its price as the second.

Information

The WooCommerce request is made in AJAX. So we have access to the values of the form stored in the $_POST variable, more precisely in the $_POST['post_data'] key that will have to be deserialized. We then use a homemade function called get_wc_posted_data() to access these values more quickly.

Make our new fields visible to the eyes of WooCommerce

When sending a (valid) order to WooCommerce, the processed form fields are limited only to those existing / known by WooCommerce. This is a security layer created by WooCommerce. It allows the plugin to completely ignore form values that would not come from WooCommerce or from extensions installed on the site.

This prevents malicious users from editing the data sent in an attempt to inject malicious code into the checkout process.

PHP

Fortunately for us, we can take advantage of the woocommerce_checkout_posted_data filter to indicate to WooCommerce that such or such field of the sent form can be used for our custom logic. In our case, we add two keys => values to the data array:

  • the msk-urgent-order key to know if the emergency checkbox was checked by the buyer,
  • and the msk-urgency-level key to know the level of urgency chosen by the buyer

Attention

Even if our values have been validated upstream before the final submission of the form, remember to clean up the values received with the sanitize_...() functions of WordPress.

This data array therefore contains the values from the freshly sent checkout form. It will be used in the next step.

Save the fields values everytime an order is placed

WooCommerce has created a new order, it’s time to save the values of our custom fields!

PHP

We take advantage of the woocommerce_checkout_update_order_meta hook that runs only after the creation of an order by WooCommerce in the front-end buying process.

Our hooked function will receive the ID of the created order but also the $data array from the order form. It is in this array that we have just saved our vital data regarding the urgency of the order.

In our case, we save these two custom data in the metadata of the order to keep in memory the user’s choice.

Nos 2 métadonnées visibles dans le back-office de la commande créée

It is at this level that you will be able to really execute custom actions for a personalized e-commerce site. Sending an e-mail, delegating a process to an API, classifying the order… it’s up to you to process the different cases with the fields values that have just been added to the checkout form.

Conclusion

In a few steps, we successfully added custom fields on the WooCommerce order form. This custom shopping tunnel of our e-commerce shop will undoubtedly delight your most eager buyers 🤩!

Please share with us in the comment section about the different ways you used this tutorial 🙂

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