Chapter 1 - Introduction

15 years ago, writing unit tests for a project was not a widespread practice in the PHP world. As a matter of fact, PHPUnit only reached version 1.0 in mid-2004. How did we know our projects were bug-free back then? By clicking around, literally. After fixing a bug, or adding a new feature, developers would browse their applications like crazy to check that nothing was broken. Needless to say, this was a tedious, boring, and error-prone process. After a while, developers and project managers were doing less manual testing and bugs were "unintentionally" deployed to production servers and regressions were common. In a way, customers and end-users were in charge of the quality assurance.

Nowadays, everyone writes unit and/or functional tests for their PHP applications. At least, everyone should as we now have great tools like PHPUnit, Behat, Codeception, Selenium, and more. If you are not writing tests, you probably feel bad about it, right?

People don't write tests because it's fun or easy. We write tests because the cost of a bug or a regression is gigantic. A bad user experience has a direct, negative impact on business reputation and damages a company's bottom line. This is nothing new. According to Boehm and Basili's "Software Defect Reduction Top List" published in 2001, the cost of fixing a bug is 15 times more expensive after release (from $937 in development to $14,102 in production).

What about performance? How many developers continuously test the performance of their applications? According to my own experience, not that many. What's more, nobody feels ashamed for not writing performance tests; probably because the existing tools are not good enough. Unfortunately, performance issues have the same impact as bugs: bad user experience leading to less engagement and revenue loss.

How do you ensure that the performance of your applications is good enough before going to production? Are you using a load-testing tool? Are you benchmarking your code? How do you find bottlenecks?

We've all used the simple microtime() PHP built-in function for testing performance. I've used it myself for many years to try to optimize my PHP projects. It is frustrating to say the least. microtime() can only tell you part of the story: some code takes more time than it should. This is okay, but it cannot tell you why the code is slow or how you can improve it. Even if you find a bottleneck, validating a fix is difficult as numbers can vary widely from one run to the next, and the seemingly innocuous changes can have negative impacts on other parts of the code.

The point is that it is easy to make stupid performance mistakes: n + 1 queries when using an ORM is the first one that comes to mind, but they are many other ones.

The n + 1 query problem occurs when getting children records of a main record with an ORM. When lazy-loading is enabled, the ORM will get the main record from the database and then issue n additional queries for the children records; the more children you have, the more queries are issued, and the slower the code becomes.

Performance management is not something you do once, just before you release your code. In order to be effective, performance management must be included in your day-to-day workflow via deep integrations into your development stack. That is what I'm going to write about in this series.

Good tools go a long way. Some solutions have been around for many years, but thanks to Blackfire, many more people are now optimizing their projects dramatically:

In the next 23 chapters, I will guide you through Blackfire's features and discuss how you can leverage Blackfire to better test your application's performance in an automated and continuous way. You will also learn that Blackfire is not just about performance; it is also a great tool to help you achieve better code quality, improved security and best practices enforcement.

But first, why is performance so important? According to Google: 53% of visits are abandoned if a mobile site takes longer than 3 seconds to load. Your customer is gone, probably forever. If your web applications are not fast enough, you will lose both customers and revenue. That's why performance optimization is key to success. Ready to learn more?