Travis and Composer and virtPHP, oh my!

I recently ran into an issue with one of my repos on GitHub when integrating it with Travis. When I installed dependencies with Composer and ran the PHPUnit tests on my local system running Ubuntu 13.10 and its stock PHP 5.5.3 apt package, they passed. However, I'd configured Travis to also do this under current 5.3 and 5.4 versions as well.

In the first build, everything worked fine under 5.4 and 5.5, but upon getting to the composer install instruction to install project dependencies and PHPUnit, the job for 5.3 failed with some rather unintuitive output from Composer that implied it didn't recognize the platform package requirement that I'd provided for the minimum PHP version.

Your requirements could not be resolved to an installable set of packages.
Problem 1
\- The requested package php could not be found in any version, there may be a typo in the package name.

Side note: While Travis does support Composer, the version of it available by default when running a job is frequently behind the current build. I've brought this up with them, but it doesn't seem they've addressed it as of this writing. In any case, it's easy enough to work around by including a composer self-update instruction as part of the build like so. This ensures that you won't be affected by any recently fixed bugs in Composer.

Since the cause of my issue wasn't immediately obvious from Composer's output, my first thought was that I needed to begin my attempt at troubleshooting the issue by replicating it on my local machine. My second thought was that seemed like an abysmally miserable prospect, as it would require that I have several different versions of PHP installed other than the current one on my system.

I'd heard recently about a new project recently via Twitter called virtPHP that purported to be PHP's answer to virtualenv for Python or rvm for Ruby. Thinking that my situation seemed a great use case for it, I proceeded to install it.

First, you have to read a bit past the cursory installation instructions on the landing page of virtPHP's web site, particularly the "Using phpenv and php-build" section of virtPHP's README file including the portion on package requirements. virtPHP doesn't accomplish this great feat all on its own. It actually builds on two other existing projects by Christoph Hochstrasser, phpenv and php-build, and functions (in a rather PHP-like vein) more like glue to make working with these projects and managing what they produce easier. More specifically, it provides support for things like differing per-project PHP, PECL, and PEAR configurations.

In reality, all I ended up needing for what eventually proved to be a rather quick-and-dirty sort-of use case was phpenv and php-build alone, though I suspect virtPHP will be indispensable when I inevitably need a more long-term setup like this. Installing all three based on the installation instructions in their README files was fairly straightforward. I used them to create three PHP installations of the versions used on Travis (5.3.27, 5.4.25, and 5.5.9 as of this writing) and to quickly switch between them to re-run the composer install command that had failed on Travis, which consistently failed under 5.3 and worked under 5.4 and 5.5 on my local system.

Eventually, I opened the composer.json file and realized the problem: I'd misrecalled the minimum PHP version I'd set for my project to be installed as 5.3 when I'd actually set it to 5.4. Composer appropriately, though perhaps not intuitively, reacted by outputting errors when the local environment was running 5.3, a PHP version that did not meet the requirement I'd set in composer.json. In poking around, I found that this sort of user error is not entirely uncommon. Once I changed the requirement to 5.3 and pushed it to GitHub, the next Travis build succeeded for all PHP versions I'd specified.

So, thanks to the folks behind virtPHP for producing this project. I suspect I'll be making more use of it in the future.