I believe that this is the same PHP. You can see the official php.net documentation on IIS installations here:
http://php.net/manual/en/install.windows.iis7.php
You can even create or install the PHP you want and link it to IIS manually (so it will be the same PHP as you anywhere else). Using MS installer could they fake PHP? Yes. Did they do it? I seriously doubt it.
One of the main differences is the extensions available in IIS. Like the way they offer Windows Cache instead of APC. However, I believe that in most cases all extensions are for extensions.
http://php.net/manual/en/book.wincache.php
So you can find a completely different ecosystem of extensions, but the main language looks exactly the same.
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