Pusher not triggering event in php

I am trying to trigger a pusher event but it's not working.

$data['message'] = 'Hello World';
$pusher->trigger('my-channel', 'my-event', $data);

I don't know what's wrong. Can you please help?

I checked errors on the pusher. It is not having any errors. Can you please help.

via Chebli Mohamed