php webhook not responding to Stripe test event - php

Question

I've setup a basic webhook php page as modeled on the stripe documentation and listed below. When I send a test event from the Stripe webhooks dashboard, stripe responds "Test webhook sent successfully" with a blankk reponse. However, the output log file is not written to, no email is sent and there is nothing logged to the http server error log or the php error log. My php version is 5.3.3. What am I doing wrong?
<?php
error_reporting(15);
// Set your secret key: remember to change this to your live secret key in production
// See your keys here: https://dashboard.stripe.com/account/apikeys
require_once('vendor/autoload.php');
\Stripe\Stripe::setApiKey("secret_test_key");
$handle = fopen("webhook.log","a");
// Retrieve the request's body and parse it as JSON
$input = file_get_contents("php://input");
$event_json = json_decode($input);
// Do something with $event_json
if (fwrite($handle, $event_json) === FALSE) {
mail("mike#example.com","Cannot write to webhook.log","");
echo "Cannot write to webhook.log";
exit;
}
mail('mike#example.com','Webhook Event',$event_json);
header(':', true, 200);
//http_response_code(200); // PHP 5.4 or greater
?>

Answer 1

You have a few potential problems. As a quick rule of thumb, the best way to debug this is to start by triggering the event yourself, which you can do simply by loading up your webhook url in a browser yourself. Then you can test it directly and make sure it is doing what you expect it to be doing. There are obviously two possibilities:
Stripe is not triggering your webhook handler for some reason
Your handler is not properly logging itself
The latter first: it could be that Stripe is triggering your handler but it isn't logging that fact successfully. This would mean that both your email logging and file logging are failing. That is actually quite possible. Email logging with the mail function is actually very unreliable, unless you know for a fact that it works. Mail sent with the mail function is dropped silently by most modern email systems (gmail, etc) unless you have your DNS records properly configured, which most people don't. So unless you know for sure that your mail attempt is working properly, it probably isn't. If you also happen to have a permission issue in your attempt to write to a log file (which is not uncommon for a newly setup server), your logs could simply be failing. The easiest way to check that is to load up the webhook URL in a browser yourself. That way you know it is being triggered, and can know for sure if the issue is improper logging or Stripe not calling your webhook.
If you determine for sure that stripe isn't calling your webhook, the most likely culprit would be an invalid HTTPS certificate. Is your webhook connected via HTTPS (it should be)? If so, is it a valid certificate? You can tell your browser to ignore an invalid certificate when you browse your own site, but stripe will simply refuse to send the request if it encounters an invalid certificate.
If none of the above fixes it then it will be time for more digging, but I would start with those: they are probably the most likely problems.

Answer 2

The solution is that $event_json is an object and the fwrite failed because it expects a string not an object. By converting to an array and then serializing I was able to both write to the log and send the email.
$event_json = (array)json_decode($input);
$event = serialize($event_json);