Php – FastCGI Error when installing PHP on IIS7.5

I'm trying to install MediaWiki on a Win2008r2 server, but can't manage to install PHP. Here's what I did:

• Grabbed a Zip archive of PHP and unzipped it into C:\PHP.
• Created two subdirs: c:\PHP\sessiondata and c:\PHP\uploadtemp.
• Granted modify rights to the IUSR account for the subdirs.
• Copied php.ini-production as php.ini
• Edited php.ini and made the following changes:


fastcgi.impersonate = 1
cgi.fix_pathinfo = 1
cgi.force_redirect = 0
open_basedir = "c:\inetpub\wwwroot;c:\PHP\uploadtemp;C:\PHP\sessiondata"
extension = php_mysql.dll
extension_dir = "./ext"
upload_tmp_dir = C:\PHP\uploadtemp
session.save_path = C:\php\sessiondata

• Install Web server role, selected CGI and HTTP Redirection options.

• In the Handler Mappings:

  • Added Module Mapping. Entered the following values:
  • Path = *.php, Module = FastCgiModule, Executable = c:\php\php-cgi.exe, Name = PHP via FastCGI.

• Created a test page into wwwroot directory: phpinfo.php and set the contents like this:
  
< ?php phpinfo(); ?>

• Browsed to http://localhost/phpinfo.php

But then I get:

HTTP Error 500.0 - Internal Server Error
An unknown FastCGI error occured
    Detailed Error Information
Module: FastCgiModule 
Notification: ExecuteRequestHandler 
Handler: PHP via FastCGI 
Error Code: 0x800736b1 

Requested URL: http://localhost:80/phpinfo.php
Physical Path: C:\inetpub\wwwroot\phpinfo.php 
Logon Method: Anonymous 
Logon User: Anonymous 

Does anyone know what I'm doing wrong here?
Thanks.