Installing PHP is relatively simple. To get started, you just need to download the PHP version you want to use from http://windows.php.net/download/ (for development you can the Non Thread Safe version).
Then you will have to modify the environment variable in order to add the PHP folder to the PATH of your system (for example C:Program FilesPHP). Once this path has been added, restart your terminal and type the following command to verify that the configuration is correctly done:
php --version