PHK is a library/application packager. You may think of it as a sort of 'jar for PHP'. It allows a developer to distribute and have his application run as a single file.
PHK also includes many additional features as on-the-fly decompression, file/path protection, optional checksum validation, meta-packaging and an amazing 'webinfo' mode which allows users to display everything about a package, its licence, documentation and more, without having to extract anything from the archive file. The 'webinfo' mode acts as an embedded micro-website whose pages can be customized at will by the package author.
PHK includes an autoload manager which extracts the symbols from your source files at package creation time, and automatically includes the appropriate code when it is needed at runtime.
The documentation is not complete yet but already contains everything you need to start enjoying PHK.
PHK is free (PHP license) and can be found at http://www.tekwire.net/joomla/products/phk