How do I install a custom app from the admin panel correctly in shopify?

I need to make a custom app (previously a private app). and I have already registered this app in the admin panel of the site. NOT from partners.

Also, I have already received the keys and token. But now I’m trying to figure out what to do next, to start writing code in php.

I am using these instructions, and I got to the step of specifying the command:

shopify app create php 

but I get an error:

PHP is required to create an app project. For installation instructions, visit:
https://www.php.net/manual/en/install.php

Can you tell me how to install php in this case? And do I need to follow the above instruction at all, because I’m creating a custom app from the admin panel of the store!

I’m confused, please help.

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