<?php
/**
 * Add custom WooCommerce checkout fields for administrator users.
 *
 * @param   array   $fields The existing billing fields.
 * @return  array   $fields The updated billing fields.
 */
function custom_woocommerce_checkout_fields( $fields ) {

    // Get the current user
    $current_user = wp_get_current_user();

    // Check if the current user is an administrator
    if ( in_array( 'administrator', (array) $current_user->roles ) ) {

        // Get the saved license number for the current user
        $saved_license_no = $current_user->license_no;

        // Add the custom fields to the billing fields array
        $fields['billing_licenseno'] = array(
            'label'       => __( 'NIF/CIF', 'woocommerce' ),
            'placeholder' => __( 'B12345678', 'woocommerce' ),
            'type'        => 'text',
            'required'    => true,
            'clear'       => false,
            'default'     => $saved_license_no,
            'class'       => array( 'form-row-wide' ),
            'priority'    => 25,
        );

        $fields['billing_customcheckbox'] = array(
            'label'         => __('Tengo Recargo (Tengo Recargo de Ekivalencia)', 'woocommerce'),
            'type'          => 'checkbox',
            'required'      => false,
            'clear'         => true,
            'default'       => 0,
            'class'         => array('form-row-wide'),
            'priority'      => 30,
        );
    }
    
    return $fields;
}
add_filter('woocommerce_billing_fields', 'custom_woocommerce_checkout_fields');

/**
 * Filters the WooCommerce order formatted billing address.
 * @param   array   $address The array of address.
 * @param   object  $order The order object.
 * @return  array   The updated array of address.
 */
function add_custom_woocommerce_order_fields( $address, $order ) {
    // Get the license number from the order meta.
    $address['licenseno'] = $order->get_meta( '_billing_licenseno' );

    // Get the custom checkbox value from the order meta.
    $address['customcheckbox'] = $order->get_meta( '_billing_customcheckbox' ) ? __( 'SI', 'text-domain' ) : __( 'NO', 'text-domain' );

    return $address;
}
add_filter( 'woocommerce_order_formatted_billing_address', 'add_custom_woocommerce_order_fields', 10, 2 );

/**
 * Saves the billing custom checkbox value on customer save address.
 * @param   int     $customer_id The customer ID.
 * @param   string  $load_address The address type.
 * @return  void
 */
function save_billing_custom_checkbox( $customer_id, $load_address ) {
    if ( isset( $_POST['billing_customcheckbox'] ) ) {
        // Sanitize the custom checkbox value.
        $checkbox_value = sanitize_text_field( wp_unslash( $_POST['billing_customcheckbox'] ) );

        // Update the user meta with the custom checkbox value.
        update_user_meta( $customer_id, 'billing_customcheckbox', $checkbox_value );
    } else {
        // If the custom checkbox value is not set, update the user meta with 0.
        update_user_meta( $customer_id, 'billing_customcheckbox', '0' );
    }
}
add_action( 'woocommerce_customer_save_address', 'save_billing_custom_checkbox', 10, 2 );

/**
 * Filters the WooCommerce localisation address formats.
 * @param   array   $address_formats The array of address formats.
 * @return  array   The updated array of address formats.
 */
function custom_localisation_address_formats( $address_formats ) {
    
    foreach ( $address_formats as $country_code => $address_format ) {
        $address_formats[ $country_code ] = str_replace(
            "{name}",
            "{name}\n{licenseno}\n{customcheckbox}",
            $address_formats[ $country_code ]
        );
    }
    
    return $address_formats;
}
add_filter( 'woocommerce_localisation_address_formats', 'custom_localisation_address_formats', 50, 1 );

/**
 * Filters the WooCommerce formatted address replacements.
 * @param   array   $replacements The array of address replacements.
 * @param   array   $args The array of arguments.
 * @return  array   The updated array of address replacements.
 */
function formatted_address_custom_replacements( $replacements, $args ) {
    $replacements['{licenseno}'] = ! empty( $args['licenseno'] ) ? $args['licenseno'] : '';
    $replacements['{customcheckbox}'] = ! empty( $args['customcheckbox'] ) ? $args['customcheckbox'] : '';

    return $replacements;
}
add_filter( 'woocommerce_formatted_address_replacements', 'formatted_address_custom_replacements', 10, 2 );

测试它，让我知道任何变化或如果错误occure

要在WooCommerce账单数据中显示新字段的数据，您需要添加自定义代码：
1.将新字段添加到帐单表单
1.将新字段数据保存到订单 meta数据中
1.在订单详细信息页面、电子邮件和其他相关位置显示新字段数据
下面是一个示例代码片段，演示了如何将公司名称的新字段添加到WooCommerce账单表单并将数据保存到订单 meta：

// Step 1: Add new field to billing form
add_filter( 'woocommerce_billing_fields', 'add_company_name_field' );

function add_company_name_field( $fields ) {
    $fields['billing_company_name'] = array(
        'label'       => __( 'Company Name', 'woocommerce' ),
        'required'    => false,
        'class'       => array( 'form-row-wide' ),
        'clear'       => true,
        'priority'    => 25,
    );

    return $fields;
}

// Step 2: Save new field data to order meta
add_action( 'woocommerce_checkout_create_order', 'save_company_name_field' );

function save_company_name_field( $order ) {
    if ( ! empty( $_POST['billing_company_name'] ) ) {
        $order->update_meta_data( '_billing_company_name', sanitize_text_field( $_POST['billing_company_name'] ) );
    }
}

// Step 3: Display new field data in relevant places
add_filter( 'woocommerce_order_formatted_billing_address', 'display_company_name_in_billing_address', 10, 2 );

function display_company_name_in_billing_address( $address, $order ) {
    $company_name = $order->get_meta( '_billing_company_name', true );

    if ( $company_name ) {
        $address .= "\n" . $company_name;
    }

    return $address;
}

在这个示例代码中，我们使用woocommerce_billing_fields过滤器将“公司名称”的新字段添加到账单表单。然后，我们使用woocommerce_checkout_create_order操作将该字段中的数据保存到订单 meta数据中。
最后，我们使用woocommerce_order_formatted_billing_address过滤器在订单详情页面和电子邮件的账单地址部分显示公司名称。
您可以根据需要自定义字段名称、标签和 meta密钥。此外，您可能需要更新使用计费数据的其他函数，以包括新的字段数据。