Filter for customer billing details required field.

Source

File: /inc/class-wp-travel-form-handler.php
Used by: /inc/class-wp-travel-form-handler.php

Parameters
$fields

Example:

function prefix_wp_travel_save_customer_billing_details_required_fields( $fields ) {
    $fields[‘customer_zip_code’] = ‘ __( 'Your ZIP Code',
    'wp-travel' )’;
    return $fields;
}
add_filter( 'wp_travel_save_customer_billing_details_required_fields', 'prefix_wp_travel_save_customer_billing_details_required_fields' );