How to Run PHP Files
If you double click on a HTML file (files with .html or .htm extension), it would open on your web browser. But same won’t happen if you double clicked on a PHP file (probably it would open in an editor). The reason is PHP files first need be processed in a web server before sending their output to the web browser.
Therefore before running PHP files, they should be placed inside the web folder of a web server and then make a request to desired PHP file by typing its URL in the web browser. If you installed a web server in your computer, usually the root of its web folder can be accessed by typing http://localhost in the web browser. So, if you placed a file called hello.php inside its web folder, you can run that file by calling http://localhost/hello.php.
Web folder can be changed based on your web host (if you hosted your web site online) or the method you installed the web server in your computer. If you used XAMPP to install Apache (web server) in your computer then the web folder would be htdocs which is under the root directory of XAMPP.