In this recent post to his site Phil Sturgeon has a reminder that you should select the dependencies for your packages wisely, and not just because they're "cool."

When I say "make sure it is worth it" I mean, don't just switch your arrays from array() to [] just because it looks cool. That was the extent of my original tweet, because I've seen a few packages doing that and it annoyed me immensely. [...] Suffice it to say, if you require a user to upgrade their version of PHP simply so you can use some syntactical sugar inside a package that nobody else is even going to be looking at, then you're an idiot. Beyond that, you're actually hurting the community.

He notes that, by requiring users that are currently only at 3.1% of PHP installs to upgrade to 5.4 just to use your library is a quick way to not have your library used. He points out that PHP 5.4 is "more than just []" for arrays and includes a reminder that several projects are still in PHP 5.3-compatibility mode just because that's the widest audience. He also briefly touches on the "push it forward" comments that people have used to justify 5.4-only packages, but notes that it's still not as much up to the developer as it is the web host.