Is there a ready-made example of implementing a callback after an application on the site falls?

Question

PHP

Hello everyone,
does anyone have a ready-made example of the implementation of the callback function from the task (via api), when a visitor leaves a request on the site through the form, immediately after the request arrives at the mail, the application automatically makes a call to both the operator and the visitor.
I tried to implement it myself according to their documentation, but at some point I make a mistake and I can’t understand, maybe someone has a ready-made implementation example