title: Implement notification in angular 5
body: <p>I have web application which uses php laravel as backend and angular 5 as frontend. I need to implement push notifications on my application. I have been using 'OneSignal' for notifications. Accordingly I used the web custom code in angular, but I need to know that is there any way that I could call my php web service as soon as I receive the notification. How would I come to know in angular that I have received a notification so that I could call my web service?</p>