In command prompt type below

set PATH=%PATH%;C:\path\to\php

Where C:\path\to\php is the folder where your php.exe file is located. After this run

C:\>php -v

than you will see something like

PHP 7.3.6 (cli) (built: May 29 2019 12:11:00) 

UPDATE:

If you find that when you restart your computer, this solution will not work anymore:

Set the Path like as following:

Step 1 - Click on the Windows icon

Step 2 - Click on the Settings icon

Step 3 - Click on System

Step 4 - Click on About

Step 5 - Click on System info

Step 6 - Click on Advanced system settings

Step 7 - Click on Environment variables...

Step 8 - Select Path row and then click Edit

Step 9 - Click New and then click Browse, then in the next panel which will open you need to select the folder you want in the Path. For the initial premise of this guide i will add the folder C:\Users\NewFolderInPath

Note: Replace your PHP installed path(e.g:C:\Program Files\php) with the above path .

Step 10 - Click OK and click every OK button you will encounter to close every previous windows.

Try running the following at the command line.

To just get the version information:

php -v

Or to get a lot of info:

php -i

It should give you all information you need about the php install.