Box is a library and command line application for simplifying the PHAR creation process. [Features include] creating new PHARs with a simple configuration file, add and replace files in existing PHARs, extract existing PHARs, with option to cherry pick files and verify PHAR signatures.
The project is still relatively young but it looks like it's off to a good start. Phar files are a powerful tool to have in a PHP developer's arsenal but developing them can be a pain. Hopefully something like this can make life easier.