can we use in php based site

suppose i have an ecom site in php
now i want to use this plugin but thats not possible in that site
so i shall install this as a separate site or subdomain and just link in main site , so this will work right ?

this plugin does have checkout feature so how to add gateway to checkout or that is not available ? do u have a video to check the same. please let us know the same, we want to buy the plugin soon