YaBook is a simple but powerful guestbook running on PHP 5. It features easy installation and customization, multi-language support, an administration interface, and email notifications on new postings. YaBook's design uses a template system so it can be easy integrated into your page. YaBook ist built on the Sourdough framework, a web application framework for PHP 5. Various database systems are currently supported, e.g. MySQL, PostgreSQL, MSSQL, SQLite.