wxPHP is a wrapper implementation of the wxWidgets for PHP to provide a cross-platform GUI library. In the past there was the PHP-GTK project to provide GTK2 support for PHP, but that project has basically stalled while now there's this vibrant wxPHP project for those wanting to create desktop user-interfaces with PHP.
One of the wxPHP developers wrote into Phoronix hoping to get some attention for the project and said:
wxPHP is a binding of wxWidgets that lets you develop cross-platform desktop applications using PHP. This applications can be executed on Windows, Linux and MacOSX using the same code base. The PHP language has grown in the community mostly as a web programming language, but this project revives and complements a usage scenario of the language that was previously promoted by the PHP-GTK project.
The authors of the project believe that you can easily use your existing php web/cli applications code base and logic to create native graphical user interfaces that makes them more accessible and easier to use. In contrast to its older brother PHP-GTK, wxPHP applications look native in all platforms, has less dependencies which makes the extension easier to build and the code is compatible with latest PHP releases.
The latest binaries for v126.96.36.199 includes fixes from v188.8.131.52 which didn't see a binary release. A list of applications developed with the extension can be found at this page also screenshots comparing the three supported platforms.
The source code of the project is hosted at GitHub and binary builds for Ubuntu, Windows, Mac OS X, and the Raspberry Pi are available at SourceForge. Also the extension can be installed from PECL. For rapid application development, PHP support was implemented in wxFormBuilder making it easier to design graphical user interfaces.