I was first introduced to the concept of webhooks via a 2009 blog post by John Herren, a former colleague at Zend. At the time, they were in their infancy; today, they're ubiquituous, as they provide a mechanism for a service to notify interested parties of events. This saves traffic; instead of consumers polling an API for event changes, the service notifies them directly. It also means that the consumer does not need to setup things like cronjobs; they instead setup a webhook endpoint, register it with the service provider, and their application takes care of the rest.

The thing is, handling a webhook can often lead to additional processing, and you are expected to send an immediate response to the provider indicating you received the event.

How can you achieve this?

Sites I build often utilize cronjobs to periodically pull in data from other sources. For example, I might want to poll an API once a day, or scrape content from another website once a month. Cronjobs are a perfect fit for this.

However, cron has a few problems:

• If the job is writing information into the file tree of your web application, you need to ensure permissions are correct, both at the filesystem level, and when writing the cronjob (e.g., running it as the same user, or changing permissions on completion).
• If you are running console tooling associated with your PHP application, you may need to worry about whether or not particular environment variables are in scope when you run the job.
• In containerized environments, usage of cron is strongly discouraged, as it means running another daemon. You can get around this with tools such as the s6-overlay, but it's another vector for issues.

Since most sites I build anymore use mezzio-swoole, I started wondering if I might be able to handle these jobs another way.

Have you used Node.js?

For those of my readers unfamiliar with Node.js, it's a server-side JavaScript framework that provides the ability to create, among other things, network services. To do so, it provides an event loop, which allows for such things as asynchronous processing.

In the PHP ecosystem, a group of Chinese developers have been creating an extension that provides many of the same capabilities as Node.js. This extension, called Swoole, allows you to create web servers with asynchronous capabilities. In many cases, the asynchronous capabilities are handled via coroutines, allowing you to write normal, synchronous code that still benefits from the asynchronous nature of the system event loop, allowing your server to continue responding to new requests as they come in!

We've been gradually adding and refining our Swoole support in Expressive, and recently issued a stable release that will work with any PSR-15 request handler. In this post, I'll enumerate what I feel are the reasons for considering Swoole when deploying your PHP middleware application.