GuzzleJSON

<?php

error_log(file_get_contents('php://input'));

/*
[15-Jul-2018 01:13:26 UTC] {"collection_id":"<your-collection-id-here>","email":"[email protected]","description":"BB","mobile":"60123456789","name":"AA","amount":2000,"callback_url":"http:\/\/yourwebsite.com\/return_url"}
*/