以下代码根据购物车中虚拟产品的数量注册自定义字段：

function cart_has_virtual_product() {
    if ( ! is_a( WC()->cart, 'WC_Cart' ) ) {
        return 0;
    }

    $virtual_product_count = 0;

    foreach ( WC()->cart->get_cart() as $cart_item_key => $cart_item ) {
        $product = $cart_item['data'];
        if ( $product->is_virtual() ) {
            $virtual_product_count += $cart_item['quantity'];
        }
    }
    return $virtual_product_count;
}

add_filter('woocommerce_form_field', 'addHeadingsInBetweenFormFields', 10, 4);

function addHeadingsInBetweenFormFields($field, $key, $args, $value = null) {

  if (is_checkout() & $key === 'order_jmeno_ucastnika') {
    $a = '<h3>Údaje o účastníkovi kurzu</h3>';
    return $a . $field;
  }
  return $field;

}


function add_custom_checkout_fields( $fields ) {
    $virtual_product_count = cart_has_virtual_product();

    for ( $i = 1; $i <= $virtual_product_count; $i++ ) {
        $fields['order']['order_jmeno_ucastnika' . $i] = array(
            'label'     => 'Jméno účastníka ' . $i,
            'placeholder'   => 'Jméno Příjmení',
            'required'  => true,
            'class'     => array( 'form-row-wide' ),
            'clear'     => true
        );

        $fields['order']['order_email_ucastnika' . $i] = array(
            'type'      => 'email',
            'label'     => 'E-mail účastníka ' . $i,
            'placeholder'   => '',
            'required'  => true,
            'class'     => array( 'form-row-wide' ),
            'clear'     => true
        );

       $fields['order']['order_title' . $i] = array(
            'label'     => 'Titul/y' . $i,
            'placeholder'   => 'Titul/y',
            'required'  => false,
            'class'     => array( 'form-row-wide' ),
            'clear'     => true
        );

$fields['order']['order_birthdate' . $i] = array(
    'type'      => 'date',
    'label'     => 'Datum narození' . $i,
    'placeholder'   => 'DD.MM.RRRR',
    'required'  => true,
    'class'     => array( 'form-row-wide' ),
    'clear'     => true
);
    }

    return $fields;
}

然后这些字段转到管理中的订单详细信息：

function save_custom_checkout_fields( $order_id, $posted_data ) {
    $virtual_product_count = cart_has_virtual_product();

    for ( $i = 1; $i <= $virtual_product_count; $i++ ) {
        if ( isset( $_POST['order_jmeno_ucastnika' . $i] ) ) {
            update_post_meta( $order_id, 'order_jmeno_ucastnika' . $i, sanitize_text_field( $_POST['order_jmeno_ucastnika' . $i] ) );
        }
        if ( isset( $_POST['order_email_ucastnika' . $i] ) ) {
            update_post_meta( $order_id, 'order_email_ucastnika' . $i, sanitize_email( $_POST['order_email_ucastnika' . $i] ) );
        }
        if ( isset( $_POST['order_title' . $i] ) ) {
            update_post_meta( $order_id, 'order_title' . $i, sanitize_text_field( $_POST['order_title' . $i] ) );
        }
        if ( isset( $_POST['order_birthdate' . $i] ) ) {
            update_post_meta( $order_id, 'order_birthdate' . $i, sanitize_text_field( $_POST['order_birthdate' . $i] ) );
        }
    }
}
add_action( 'woocommerce_checkout_update_order_meta', 'save_custom_checkout_fields', 10, 2 );

然后当订单完成时，我们应该向字段中的所有收件人发送电子邮件'order_email_ucastnika。这就是问题所在。当我有收件人设置为帐单电子邮件，它工作正常。但现在电子邮件不发送。

function send_zoom_link_on_order_complete( $order_id ) {
    $order = wc_get_order( $order_id );
    $items = $order->get_items();
    $virtual_product_count = cart_has_virtual_product();

    foreach ( $items as $item ) {
        $product_id = $item->get_product_id();
        $zoom_link = get_post_meta( $product_id, 'zoom_link', true );
        $custom_info = get_post_meta( $product_id, 'custom_info', true );

        if ( $zoom_link ) {
            for ( $i = 1; $i <= $virtual_product_count; $i++ ) {
                $to = get_post_meta( $order_id, 'order_email_ucastnika' . $i, true );
                $subject = 'my subject ' . $item->get_name();
                $message = 'link: ' . $zoom_link . $custom_info;

                // add headers
                $headers = array(
                    'From: mysite.com <orders@mysite.com>',
                    'Content-Type: text/html; charset=UTF-8'
                );

                wp_mail( $to, $subject, $message, $headers );
        }
    }
}
}
add_action('woocommerce_order_status_completed', 'send_zoom_link_on_order_complete');

你觉得会出什么问题吗？