Mucking around with the format parameter on a siteinfo call I got this
with "action=query&meta=siteinfo&format=wddx"
This was just now, around 0220 GMT, September 29, and the site is
English Wikipedia.
<?xml version=\"1.0\"?>
<wddxPacket version=\"1.0\">
<header/>
<data>
<struct>
<var name=\"error\">
<struct>
<var name=\"code\">
<string>internal_api_error_MWException</string>
</var>
<var name=\"info\">
<string>Exception Caught: Internal error in
ApiFormatWddx::slowWddxPrinter: Unknown type boolean</string>
</var>
<var name=\"*\">
<string>#0
/usr/local/apache/common-local/wmf-deployment/includes/api/ApiBase.php(913):
wfDebugDieBacktrace('Internal error ...')#1
/usr/local/apache/common-local/wmf-deployment/includes/api/ApiFormatWddx.php(109):
ApiBase::dieDebug('ApiFormatWddx::...', 'Unknown type bo...')#2
/usr/local/apache/common-local/wmf-deployment/includes/api/ApiFormatWddx.php(95):
ApiFormatWddx->slowWddxPrinter(false, 16)#3
/usr/local/apache/common-local/wmf-deployment/includes/api/ApiFormatWddx.php(95):
ApiFormatWddx->slowWddxPrinter(Array, 12)#4
/usr/local/apache/common-local/wmf-deployment/includes/api/ApiFormatWddx.php(95):
ApiFormatWddx->slowWddxPrinter(Array, 8)#5
/usr/local/apache/common-local/wmf-deployment/includes/api/ApiFormatWddx.php(62):
ApiFormatWddx->slowWddxPrinter(Array, 4)#6
/usr/local/apache/common-local/wmf-deployment/includes/api/ApiMain.php(454):
ApiFormatWddx->execute()#7
/usr/local/apache/common-local/wmf-deployment/includes/api/ApiMain.php(434):
ApiMain->printResult(false)#8
/usr/local/apache/common-local/wmf-deployment/includes/api/ApiMain.php(248):
ApiMain->executeAction()#9
/usr/local/apache/common-local/wmf-deployment/includes/api/ApiMain.php(232):
ApiMain->executeActionWithErrorHandling()#10
/usr/local/apache/common-local/wmf-deployment/api.php(116):
ApiMain->execute()#11
/usr/local/apache/common-local/live-1.5/api.php(3):
require('/usr/local/apac...')#12 {main}</string>
</var>
</struct>
</var>
</struct>
</data>
</wddxPacket>