3 Feb 2009 @ 2:00pm : Update on libxml2 issues
4 Mar 2009 @ 2:38pm : Conclusion of libxml2 Issues – Use PHP 5.2.9 & libxml2 2.7.3
17 Mar 2009 @ 3:05pm : WordPress & libxml2 Episode IV: A New Plugin
A gradually growing list of people have run into a very odd problem using XML-RPC methods in WordPress, where the left angle bracket ( < ) gets stripped. There's been a fair bit of discussion about this on ticket #7771. The bottom line: the behavior of the PHP XML extension when built against newer versions of libxml2 changed, such that left angle brackets get stripped when parsing XML.
There’s been some back and forth between libxml2 folks (email list) and the PHP folks (bug 45996), with no real solution for those using the tainted versions of libxml2. So what are your options if you’ve got this problem? Here’s two:
- Stick with older, known to work versions of libxml2. It’s been reported by others that libxml2 <= 2.6.32 work. I've personally only tested up to 2.6.30, which has been working fine for me.
- Build the PHP XML module against the expat parser instead of libxml2
Both of these options require some server admin abilities and know how, making them unrealistic options for many WordPress users. Undoubtedly many hosting services will role out these newer versions of libxml2 as part of their regular updates. This will leave some WordPress users with sudden errors that weren’t there before.
As this was spurred by a change in behavior by libxml2, I think the ideal solution would be to provide a backwards compatible mode that would restore the old parsing mechanism (you know, the one that doesn’t strip angle brackets). Short of that happening perhaps the XML extension for PHP will need to grow to work correctly with the new way that libxml2 works. Either way, I’d like to see PHP XML parsing work correctly again.
If you aren’t having any of these problems right now I recommend NOT upgrading libxml2 on your system until this has been sorted out.