Enzyme is an architecture for creating user-searching-user applications. Right now, it is primarily useful as a resume create/search and HR management system. However, it's potential uses are wide-ranging, and it offers PHP developers an alternative to relying on simple "keyword" searching systems.
TYPO3 CMS is a Web Content Management System which features automatic creation of navigational menus, headlines, and other dynamic graphical elements, automatic conversion and scaling of images, the ability to present different templates based on variables such as client browser or country code, support for multiple templates on a site, and a built-in password-protection option. Pages can be timed to be shown on a certain date, be hidden on a certain date or just temporarily hidden. TYPO3 supports search in SQL-databases and redesigning of a website at once is just a matter of creating a single new template.
LinPHA is an easy-to-use, multilingual, flexible photo/image archive/album/gallery written in PHP. It uses an SQL database (MySQL/PostgreSQL/SQLite) to store information about your pictures. It comes with an HTML-based installer, so you don't need experience in setting up SQL databases. Thumbnails are created as needed and stored in the SQL DB. It features complete user management, top ten statistics, hidden albums, different themes, slideshow, filemanager, uploader, watermarks, benchmark, printing, and more.
SearchAssist is a simple but practical search engine application that uses a ternary search tree. It uses Java's dynamic loading feature to make the search engine highly customizable, and uses takes Mozilla bookmarks as input. A Swing UI allows users to enter search words and view the results.