woocommerce版本：Version: 9.8.1

在my-account页面，编辑账单地址后，保存时，触发错误：

Warning: Undefined variable $field_values in C:\wamp64\www\html\wp-content\plugins\woocommerce\src\Blocks\Domain\Services\CheckoutFieldsFrontend.php on line 319

/**
 * Get posted additional field values.
 *
 * @param string  $location The location to get fields for.
 * @param string  $group The group to get fields for.
 * @param boolean $sanitize Whether to sanitize the field values.
 * @return array The posted field values and sanitized field values.
 */
protected function get_posted_additional_field_values( $location, $group, $sanitize = true ) {
    $additional_fields = $this->checkout_fields_controller->get_fields_for_location( $location );

    // phpcs:disable WordPress.Security.NonceVerification.Missing
    foreach ( $additional_fields as $field_key => $field_data ) {
        $post_key                   = CheckoutFields::get_group_key( $group ) . $field_key;
        $field_values[ $field_key ] = wc_clean( wp_unslash( $_POST[ $post_key ] ?? '' ) );

        if ( $sanitize ) {
            $field_values[ $field_key ] = $this->checkout_fields_controller->sanitize_field( $field_key, $field_values[ $field_key ] );
        }
    }
    // phpcs:enable WordPress.Security.NonceVerification.Missing
    return $field_values;
}

分析代码，是获取$additional_fields时为空，导致foreach直接跳过，造成$field_values为定义就直接返回，因此触发页面报错。

$additional_fields代表自定义额外字段，例如商家添加的自定义表单字段（如公司税号、特殊说明等）。

这应该是woo插件bug吧，我先自己修复下，到时随官方解决bug再更新。

protected function get_posted_additional_field_values( $location, $group, $sanitize = true ) {
    $additional_fields = $this->checkout_fields_controller->get_fields_for_location( $location );

        // bug修复
        // 如果没有额外字段，直接返回空数组
        if ( empty( $additional_fields ) ) {
            return array();
         }

       $field_values = array();

    // phpcs:disable WordPress.Security.NonceVerification.Missing
    foreach ( $additional_fields as $field_key => $field_data ) {
        $post_key                   = CheckoutFields::get_group_key( $group ) . $field_key;
        $field_values[ $field_key ] = wc_clean( wp_unslash( $_POST[ $post_key ] ?? '' ) );

        if ( $sanitize ) {
            $field_values[ $field_key ] = $this->checkout_fields_controller->sanitize_field( $field_key, $field_values[ $field_key ] );
        }
    }
    // phpcs:enable WordPress.Security.NonceVerification.Missing
    return $field_values;
}