PHP is a scripting programming language. PHP file has extension of *.php. You can edit it with Notepad or any other text editor.
To use PHP with QuickField Object Model and Parametric Object Interface you need to install COM module. Running PHP on windows require instulling web server. You can use WampServer - bundle of Apache server and PHP, that already has COM module.
Examples on using QuickField with PHP:
Relay dynamics simulation using PHP and ActiveField (QuickField Object Model)