Vance Lucas has a new post sharing some of his experience in setting up nginx+PHP-FPM with phar packages that he recently had with setting up a new server instance for a company. The problem showed itself as blank pages, apparently due to a feature in the Suhosin security package.
Ran into this issue when setting up a new VPS for AutoRidge. This happens when using Nginx and PHP-FPM with PHP 5.3+ and the Suhosin patch when trying to run a PHP script using a PHAR package. From what I can gather, the Suhosin patch basically blocks PHP include/require functions from executing files ending with .phar, which results in a PHP segfault that leaves no trace of any error at all.
His solution is a pretty simple one - edit the "suhosin.ini" file to allow for the opening of includes in phar files (suhosin.executor.include.whitelist). You can find out more about the Suhosin security tool on the project's website.