Go to your C:\inetpub\wwwroot directory and create a test.php file with the following content:
<?php phpinfo(); ?>
Right-click in the folder and select ‘New Text Document’ and copy the above line of text into the newly created file. Save this file as “test.php”.
Access this file from your browser (http://localhost/test.php) and it should display the PHP installation info so you will know if PHP is working correctly or not.
If that doesn’t work you may need to add *.php extension to the mappings handler: ISS Manager -> Handler Mapings -> Add Module Mapping -> (set options: *.php, fastCgiModule; path to php-cgi.exe; FastCGI).