Connecting payment means only by means of the frontend? Really?

Question

PayPal

I am a beginner frontend developer and I was given the task of integrating payment systems into the paypal, coinbase and stripe website. In general, is it really possible to do this using only the frontend? I didn’t have to connect payments yet.
The site has a field where a person enters a phone number, and by paying $ 1 he can call there. No registration is requested. Dialer via webRTC
Can you tell me which manual is sensible?

Answer 1

in paypal itself something with the word button