(Tip to
others -- never, ever use the array_key_exists() function unless you
absolutely must, and then be sure to reset() the array before you do.
Otherwise, the function call might never return!)
That sounds like a bug in PHP (or HHVM, if that's what you're using). You should file it upstream with details on how exactly to reproduce it.
--
Brad Jorsch (Anomie) Senior Software Engineer Wikimedia Foundation