PHP 5.2 is from 2006. It's stuff like this that gives PHP a bad reputation; it's next to impossible to build great stuff with 5.2 as your baseline. Not to mention the security holes! What a mess :(
Seriously. For a simple project like the API implementation of PhotoBackup, I really think I want to allow as many people to run it as possible. But should that really mean supporting software from 2006? Apparently so...
It's not PHP's problem per se, but rather problem of hosts who don't update to the newer versions. But then, if they did update often, there would be many broken websites due to breaking changes between versions; since many people are not programmers, they could lose their site if they don't know how to make the update.