On a Windows 7 development machine, I have expression web 3, PHP 5 installed

I have been using expression web and PHP for a while, and previewing php pages etc on pressing F12 (preview using local server). Suddenly on F12 all PHP pages display as blank, even a phpinfo() file. Standard html pages continue to work correctly on F12.

If I place the same page php inside the default website on inetpub and browse using localhost then the phpinfo() file works. So I know that php is installed and configured correctly for IIS.

Things I've checked:

• Gone into site settings in Expression web and confirmed that php is selected and it is pointing to the php executable
• Reinstalled php
• Checked iis that the php extension is registered.
• Copied files to a different machine with expression web and php installed and it works on.
• The strange thing is that it gives a blank (no errors) page inside expression web, but does work inside inetpub
• This was working up until recently, then suddenly stopped for no reason.