show php error message on IIS 7

With IIS7, it doesn't pass the errors through by default. It's "existingResponse" that needs to be set.

You can set it by running the following (make sure to replace {sitename} with your site name).

c:\windows\system32\inetsrv\appcmd.exe set config "{sitename}" -section:system.webServer/httpErrors /existingResponse:"PassThrough" /commit:apphost