By lwr. CC BY-NC-SA 2.0
I’ve been meaning to write this post nearly a month now, on the heels of WordPress 3.0′s release and preparing for an inevitable future discussion of when we should drop PHP 4 support. And then current events give you the hook you need to sit down and do it.
A peculiar bug sent over the mailing list for WordPress support forum moderators piqued my interest. There was an incompatibility with WordPress 3.0 and Earthlink hosting, with no known solution. Until this point I wasn’t even aware Earthlink did web hosting. I’ve enjoyed communicating with MediaTemple, GoDaddy, Network Solutions and Dreamhost on Twitter, but I couldn’t find Earthlink, so I picked up the phone and simply called their support line.
I explained who I was, and someone helpfully filed my contact information in a ticket reported by an Earthlink customer. I wasn’t expecting a response, at least not a speedy one, but the next day I received an email from Earthlink.
I give them a ton of credit for this, because the initial email I received included everything they knew, along with full access to a test server. Since the email also included the fatal error from the log, I pulled up the file and line, and realized the problem immediately.
Well, not quite. The fix was obvious, but the bug was not. I consulted with Peter Westwood and we were able to locate two seemingly relevant PHP bugs and a note in the PHP 5.1.0 changelog.
Here’s where Earthlink stops receiving credit: they were running PHP 5.0.5, released in 2005. (I may agree with WordPress supporting old versions of PHP, but that doesn’t mean I support them being used.) Apparently, there was a change in 4.4 and 5.0.5, fixed in 5.1.0, that prevented you from passing by reference into one function the return value of another function, and requiring you to assign it to a variable first.
A few things to emphasize. This affects very few installs. Our PHP 4 usage is very low as of late, and given the few reports of the issue and that they can all be tied back to Earthlink, 5.0.5 is not seen in the wild often either. So while the fix is included in WordPress 3.0.1, there is nothing we have seen that would make me think we should speed up the 3.0.1 release, which generally comes about a month after the initial release.
While we do PHP 4 compatibility testing, as of late it is limited, which has valid reasoning but is also a valid problem. Even testing under our minimum requirements, 4.3.0, would not have caught this bug, which was only in 4.4 and 5.0.5.