What causes an HTTP 405 “invalid method (HTTP verb)” error when POSTing a form to PHP on IIS?

Question

I have one form in a PHP (5.2.9-1) application that causes IIS (Microsoft-IIS/6.0) to throw the following error when POSTed:

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Answer 1

By any chance have you tried POST vs post? This support article suggests it can cause problems with IIS: http://support.microsoft.com/?id=828726