CalDAV Booking Plugin for WordPress

A WordPress plugin for appointment booking with CalDAV synchronization. Compatible with SOGo, Mailcow, Nextcloud, and other CalDAV servers.

✨ Features

• Inverse Availability System - Only explicitly marked calendar events (e.g., "VERFÜGBAR") create bookable time windows
• Multiple Meeting Types - Configure different appointment types with custom durations, colors, and descriptions
• Real-time Availability - Checks CalDAV server for current availability
• Race Condition Protection - Database-level locking prevents double bookings
• Async Processing - Fast booking response with background CalDAV synchronization
• Email Notifications - Customizable templates for customer and admin emails
• Spam Protection - Rate limiting and honeypot fields
• Responsive Design - Works on all devices
• Caching - Built-in caching for improved performance

📋 Requirements

• WordPress 5.0 or higher
• PHP 7.4 or higher
• CalDAV server (SOGo, Mailcow, Nextcloud, etc.)
• SSL certificate (recommended)

🚀 Installation

From GitHub Release

1. Download the latest release ZIP from Releases
2. In WordPress Admin, go to Plugins → Add New → Upload Plugin
3. Select the downloaded ZIP file and click Install Now
4. Activate the plugin

Manual Installation

1. Clone this repository or download the source code
2. Copy the caldav-booking-plugin folder to /wp-content/plugins/
3. Activate the plugin in WordPress Admin

⚙️ Configuration

1. CalDAV Server Settings

Go to Settings → CalDAV Booking and configure:

Setting	Description	Example
CalDAV URL	Base URL of your CalDAV server	https://mail.example.com/SOGo/dav
Username	CalDAV username	user@example.com
Password	CalDAV password	********
Calendar Path	Path to the calendar	Calendar/personal

2. Availability Keywords

The plugin uses an inverse availability system. Create events in your calendar with specific keywords to mark available time slots:

• Default keyword: VERFÜGBAR
• Additional keywords can be configured in settings

Example: Create a recurring event "VERFÜGBAR" from 9:00-17:00 on weekdays.

3. Meeting Types

Configure different appointment types:

• Name: Display name (e.g., "Quick Call")
• Duration: Length in minutes (15, 30, 45, 60, 90, 120)
• Description: Optional description shown to customers
• Color: Visual indicator

4. Email Templates

Customize email notifications with placeholders:

Placeholder	Description
{name}	Customer name
{email}	Customer email
{phone}	Customer phone
{date}	Appointment date
{time}	Start time
{end_time}	End time
{type}	Meeting type
{message}	Customer message
{site_name}	Website name

📖 Usage

Shortcode

Add the booking form to any page or post:

[caldav_booking]

Shortcode Options

[caldav_booking title="Book an Appointment" days="14" type="Consultation"]

Option	Description	Default
title	Form heading	"Termin buchen"
days	Days to show ahead	14
type	Filter to specific meeting type	(all types)

🔒 Security Features

• Nonce Verification - All AJAX requests are verified
• Input Sanitization - All user inputs are sanitized
• SQL Injection Protection - Prepared statements for all queries
• Rate Limiting - Max 5 bookings per IP per hour
• Honeypot Field - Hidden field to catch bots
• CSRF Protection - WordPress nonce system

🛠️ Development

Prerequisites

• PHP 7.4+
• Composer (optional, for development tools)
• Node.js (optional, for JS linting)

Local Development

# Clone the repository
git clone https://github.com/SKAWINSKI-GmbH/wordpress-caldav_booking_plugin.git

# Install development dependencies (optional)
composer install

# Run PHP linting
find . -name "*.php" -exec php -l {} \;

# Run PHPCS
phpcs --standard=WordPress caldav-booking.php

Creating a Release

1. Update version number in caldav-booking.php
2. Commit changes
3. Create and push a tag:

git tag v1.0.0
git push origin v1.0.0

The GitHub Actions workflow will automatically:

• Run all tests
• Build the release ZIP
• Create a GitHub Release with the ZIP attached

📁 File Structure

caldav-booking-plugin/
├── .github/
│   └── workflows/
│       └── ci.yml          # GitHub Actions CI/CD
├── assets/
│   ├── admin.css           # Admin styles
│   ├── booking.css         # Frontend styles
│   └── booking.js          # Frontend JavaScript
├── caldav-booking.php      # Main plugin file
├── LICENSE                 # MIT License
├── README.md               # This file
└── .gitignore              # Git ignore rules

🔧 Hooks & Filters

Actions

// After a booking is created
do_action('caldav_booking_created', $booking_id, $booking_data);

// After CalDAV sync completes
do_action('caldav_booking_synced', $booking_id, $result);

Filters

// Modify available slots
add_filter('caldav_available_slots', function($slots, $date, $duration) {
    return $slots;
}, 10, 3);

// Modify email content
add_filter('caldav_email_content', function($content, $booking) {
    return $content;
}, 10, 2);

🐛 Troubleshooting

Bookings not appearing in calendar

1. Check CalDAV credentials in settings
2. Use "Test Connection" button
3. Ensure WP-Cron is running (or set up a real cron job)

Slow performance

1. Enable caching in settings
2. Consider using a real cron job instead of WP-Cron:

   */5 * * * * wget -q -O - https://yoursite.com/wp-cron.php?doing_wp_cron

Emails not sending

1. Enable email debug mode in settings
2. Check wp-content/caldav-email-debug.log
3. Consider using an SMTP plugin

📄 License

This project is licensed under the MIT License - see the LICENSE file for details.

🤝 Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

1. Fork the repository
2. Create your feature branch (git checkout -b feature/AmazingFeature)
3. Commit your changes (git commit -m 'Add some AmazingFeature')
4. Push to the branch (git push origin feature/AmazingFeature)
5. Open a Pull Request

📞 Support

This plugin is provided as-is on a best-effort basis.

• Issues: GitHub Issues
• Response Time: No guaranteed response time - issues are addressed as time permits
• Commercial Support: For priority support or custom development, contact SKAWINSKI GmbH

⚠️ Note: This is an open-source project maintained in spare time. Please check existing issues and documentation before opening new issues.

🙏 Credits

Developed by SKAWINSKI GmbH