Quality Assurance in PHP Projects

This is an abstract for a chapter from a book on Quality Assurance in PHP Projects.

Incorrect application functionality is a detriment to any project, but poor performance and scalability can often lead to end-user dissatisfaction and exorbitant hardware expenses.

In the case of modern web application, expectations have made it necessary to provide responses within as little as 100 to 500 milliseconds. This puts a tremendous burden on not only achieving excellent performance, but maintaining consistent performance as code changes and new features are added.

We will review a variety of tools that can be used to test performance and scalability. While the stack will be assumed to be Linux, Apache, MySQL and PHP (LAMP), the basic skills and tools can be applied to a variety of systems (and often the ability to correctly test different system components is itself a valid test case).

An initial emphasis will be on the most basic end-to-end testing of the entire request and response cycle, but later will detail smaller benchmarks and developing custom tool sets once you require more precision. Operating System metrics are also key to ensuring an application's scalability and performance, so tools such as sar, strace, and oprofile will be covered. Because performance testing has unique requirements and challenges we will cover methodologies to correctly implement performance tests, benchmarks and the pitfalls to avoid. These include the short term assurance of accuracy, reproducing results, as well as long term goals and how to balance future expectations, growth, and priorities of an entire product or service.

Brian Shire is Facebook's technical lead for PHP internals and a developer for the Alternative PHP Cache (APC).