Hmm. The only immediately obvious item (yet probably unlikely as I think/hope PHP would whinge about this) is that your replacement headers have a quote inside them around the api.twitter.com bit which hasn't been escaped like the original one was. Also, according to their example, they *all* need to have their parameters in quotes. The error you're getting is probably better translated to "our parser barfed, so let's assume you didn't give us *everything* we wanted and ergo panic". This is an insanely annoying and common problem when trying to build this sort of thing, and unfortunately there's a trade-off between nice error messages v.s. making it easier to find the flaws in stuff for dark-hat folks, and they tend to err on the paranoid side. (Also, twitpic is being a bit odd with OAuth, as the spec recommends the use of HTTP POST variables for sending all this stuff...)