Stripe webhook: can get event ID but not type

In my webhook when I put $event_id = $event_json->id; I get the event id (example: id:evt_1EJ1NdIcP22cq9aQWsTXf8DY).

However, when I put $event_type = $event_json->type; I am expecting to get charge.succeeded or charge.failed, instead I am getting customer.source.created.

I've searched the internet up and down, can't find the answer. What should I use to get what type of charge it was (charge.succeeded or charge.failed). Maybe someone can help me solve this one.

To reiterate:
<?php
require_once('stripe/init.php');

\Stripe\Stripe::setApiKey("sk_test_xxxxxxxxxxxxxxxxxxx");

$input = @file_get_contents("php://input");

$event_json = json_decode($input);

// Get an ID just fine:
$event_id = $event_json->id;

// Should get charge.succeeded or charge.failed but it does not:
$event_type = $event_json->type;

?>