AppForMap is a collection of PHP modules for web mapping. The project comprises both clients and server for dealing with simple features, GML, WKT, WMS, WFS, PostGIS databases etc. It can also act as a backend for an OpenLayers frontend.
Map-Fu is a full-featured web mapping interface written using PHP/Javascript that can be modified and used as part of a custom web mapping application. It is designed to function as part of an open source mapping stack including UMN Mapserver.