Motivation:

• You want to understand how PHP works with IIS.
• You want to prepare a PHP or WordPress development environment on Windows.
• You want to update PHP to any version to address compatibility or security issues on Windows.

Solution:

• Install CGI for IIS on Turn Windows features on or off > Internet Information Services > World Wide Web Services > Application Development Features > CGI.
• Download VS16 x64 Non Thread Safe package under PHP 8.1 section on https://windows.php.net/download/.
• Extract the ZIP file to C:\Program Files\php-8.1.10-nts-Win32-vs16-x64 folder.
• Download the cacert.pem file and move it to the C:\Program Files\php-8.1.10-nts-Win32-vs16-x64\extras\ssl folder.
• Copy the php-.ini-development file to php.ini.
• Open the php.ini file and uncomment the following lines

  fastcgi.impersonate = 1;
  
  cgi.fix_pathinfo=1;
  cgi.force_redirect = 1 (and change the value to 0, i.e. cgi.force_redirect = 0)
  
  extension_dir = "C:\Program Files\php-8.1.10-nts-Win32-vs16-x64\ext"
  
  extension=curl
  extension=fileinfo
  extension=gd
  extension=gettext
  extension=mbstring
  extension=exif ; Must be after mbstring as it depends on it
  extension=mysqli
  extension=openssl
  extension=pdo_mysql
  
  error_log = "C:\Program Files\php-8.1.10-nts-Win32-vs16-x64\php_errors.log"
  
  error_log = syslog
  
  curl.cainfo = "C:\Program Files\php-8.1.10-nts-Win32-vs16-x64\extras\ssl\cacert.pem"
  
  openssl.capath="C:\Program Files\php-8.1.10-nts-Win32-vs16-x64\extras\ssl\cacert.pem"

• Add C:\Program Files\php-8.1.10-nts-Win32-vs16-x64 to SYSTEM PATH.
• Restart your machine.
• Open cmd and execute the command below to ensure that the PHP file can be found in the SYSTEM PATH.

  php --version

• Open IIS, click on Server name, double click on Handler Mappings > Add Module Mapping with below information.

  Request path = *.php
  
  Module = FastCgiModule
  
  Executable = "C:\Program Files\php-8.1.10-nts-Win32-vs16-x64\php-cgi.exe"
  
  Name = PHP 8.1
  
  Request Restrictions = File or folder

• Create phpinfo.php file with below content in the root website folder.

  <?php phpinfo(); ?>

• Open http://localhost/phpinfo.php URL and verify PHP information.