Introducing code quality metrics

In this section, you will learn about how to measure the quality of software in general. We will look at some of the most used metrics in the PHP world and explain what they can tell you about your code, how to gather them, and when they are useful or not.

Aspects of software quality

Before we dive into the numbers, we need to clarify one important thing first: what does software quality actually mean? Surely, everybody has a certain understanding of quality, but it might be hard to put this in words. Luckily, there are already existing models, such as the FURPS model, which was developed at Hewlett-Packard back in the 1980s. The acronym stands for the following:

• Functionality: Is the software capable of dealing with a wide variety of use cases? Has it been developed with security in mind?
• Usability: How good is the user experience? Is it documented and easy to understand?
• Reliability: Is the software available at all times?...