My suggestion: Remove support for PHP 5.2 and if a user complains tell them to change hosts. Hosting companies will upgrade real damn fast as soon as they see their numbers drop.
It doesn’t really work that way.
Don’t make the mistake of thinking that the minimum requirements is necessarily all the leverage WordPress has in this respect. WordPress currently powers approximately 25% of all websites. That’s a heck of a lot of leverage, and yes, hosts very much try to keep their users happy, and since lots of those users use WordPress, then they very much try to be compatible.
But using our users as some kind of leverage to force the issue is not a good way to behave. It alienates hosting companies, drops support for some subset of users, and generally isn’t how to keep that sustainable growth thing going.
We want people to upgrade WordPress. If we drop support for their hosting systems, then they won’t switch hosting, they’ll just not upgrade WordPress. That’s a real problem.
Not we don’t convince hosts in other ways. Simply pointing out things like PHP 7.0 is the fastest one yet, or the fact that pretty much every newer version of PHP like 5.3 and 5.4 have great speed and performance improvements is usually enough to convince hosts to start updating.
And sometimes hosts take a layered approach, with all newer servers they deploy having updated PHP versions, while leaving those older servers on the versions of PHP they have always been running, then migrating the users to newer servers one at a time.
Anyway, we are having an effect. The number of PHP 5.2 installs is down to around 13% (See https://wordpress.org/about/stats/ ), but understand that that still translates to many millions of installations. Dropping support for a few million people is not a good idea, no matter what the motivations are.
Realistically, supporting PHP 5.2 isn’t holding back WordPress. There’s no new features in PHP that WordPress relies on or really needs. Being backwards compatible is one of WordPress’ core philosophies, and it will likely stay that way until there is some really, really pressing reason to up-the-ante. That said, yes, pressuring hosts to update happens continuously, and progress, while slow, does occur.
If you as an author want to write a plugin or a theme that does not support PHP 5.2, then that is perfectly acceptable. I suggest creating a 5.2 compatible main file (for a plugin) or a functions.php file (for a theme) which checks for the PHP version first, and prevents loading the rest of the plugin/theme on 5.2 systems. This is easy to do and prevents your plugin from breaking sites, while also offering you an avenue to tell the user what the problem is and how they can fix it by asking their hosting service to upgrade them.
Edit for some additional info: We actually have better stats than what we display there. For WordPress 4.2 installs, the number of sites running PHP 5.2 is much lower, around 8%. The current most popular PHP versions, with over 75% of the installs, is 5.3 and 5.4. We track these numbers in great detail, and we are having an effect. 🙂
