How to include my payment php page on the checkout page

Hello,

I’m trying to create my own gateway class to handle BNP payment on my site.
I tested BNP payments and I have a php script working fine.

I’d like to insert this script on the checkout page (like include…)

But I don’t know how to do that with the classe that I created.

For now, the only thing that I have, when I choose this new payment mode that I created, is a button “check and submit”.

When I choose for example paypal mode, when I click on the button it leads me to paypal site.
But when I choose the payment mode I created, and when I click on the button, nothing happens.

Actually, I don’t want any button here: I only want to call my script (because this script will be generating the button)

Anyone could help ?

Thanks a lot.

https://wordpress.org/plugins/paid-memberships-pro/