How to implement access to the site api only from the application?

Question

API

There is an application for android and a server for php with a small api. Is it possible to know that the request was sent from my application?

Answer 1

Probably the simplest thing is to switch to https, so that requests cannot be easily "peeped".
To make it a little more complicated, you can use SSL Pinning to complicate the peeping process.
Another simple option is to "sign" requests - add the parameter sign=.... where ... it will be, for example, md5 from "secret string" + request parameters (you will need to decompile the application already).