Enable a custom field placeholder to Woocommerce email subject - php

Question

In Woocommerce, I have added a custom field to the checkout page using the following code:
add_action( 'woocommerce_checkout_fields', 'woo_add_conditional_checkout_fields' );
function woo_add_conditional_checkout_fields( $fields ) {
foreach( WC()->cart->get_cart() as $cart_item ){
$product_id = $cart_item['product_id'];
$fields['billing']['billing_field_newfield'] = array(
'label' => __('New Field', 'woocommerce'),
'placeholder' => _x('', 'placeholder', 'woocommerce'),
'required' => true,
'class' => array('form-row-wide'),
'clear' => false
);
}
return $fields;
}
Now, I would like to include the value that user enters in this field in the 'New Order' woocommerce email subject using {billing_field_newfield} custom placeholder.
However when I go to Woocommerce > Settings > Emails > New Order and put {billing_field_newfield} in the subject, I just get {billing_field_newfield} in the email and not its actual value.
How to add a custom dynamic placeholder to email subject in Woocommerce?

Answer 1

To add a custom active placeholder {billing_field_newfield} in woocommerce email notifications, you will use the following hooked function.
You will check before that _billing_field_newfield is the correct post meta key used to save the checkout field value to the order (check in wp_postmeta database table for the order post_id).
The code:
add_filter( 'woocommerce_email_format_string' , 'add_custom_email_format_string', 20, 2 );
function add_custom_email_format_string( $string, $email ) {
// The post meta key used to save the value in the order post meta data
$meta_key = '_billing_field_newfield';
// Get the instance of the WC_Order object
$order = $email->object;
// Get the value
$value = $order->get_meta($meta_key) ? $order->get_meta($meta_key) : '';
// Additional subject placeholder
$new_placeholders = array( '{billing_field_newfield}' => $value );
// Return the clean replacement value string for "{billing_field_newfield}" placeholder
return str_replace( array_keys( $additional_placeholders ), array_values( $additional_placeholders ), $string );
}
Code goes in function.php file of your active child theme (or active theme). It will works.
Then in Woocommerce > Settings > Emails > "New Order" notification, you will be able to use the dynamic placeholder {billing_field_newfield}…