PHP Depend - Software Metrics for PHP

Introduction

:Author: Manuel Pichler :Copyright: All rights reserved :Description: This document gives a brief introduction to PHP_Depend, software metrics in general and how they influence the quality of a software project. Beside that this document gives a brief technical introduction how PHP_Depend works internally :Keywords: Introduction, AST, Abstract Syntax Tree, PHP_Depend, Cyclomatic Complexity, CCN, quality

Introduction

PHP_Depend is a small program that performs static code analysis
on a given source base. Static code analysis means that PHP_Depend first takes the source code and parses it into an easily
processable internal data structure. This data structure is
normally called an AST (Abstract Syntax Tree), that represents the different statements and elements used in the analyzed source base. Then it takes the generated AST and measures several values, the so called software metrics. Each of this values stands for a quality aspect in the the analyzed software, observed from a very high level of abstraction, because no source was reviewed manually until now.

What is a software metric?

Okay, so what are these software metrics? Normally software metrics are really simple things. They are just the sum of some statements or code fragments found in the analyzed source. For example, the Cyclomatic Complexity or CCN of a method is just the sum of
all logical statements, like if, for etc., in the analyzed method. This means a Cyclomatic Complexity value of 23 only
says that there are 23 statements in the analyzed method. You can now take this value and compare it with your own or others
experience, when a piece of software gets unmaintainable due to its complexity.

And why should I use PHP_Depend?

That's a really good question! Why should you use a just another tool in your daily development process to perform such a simple task like building source statistics? The answer is easy.

• PHP_Depend can be used in an automated build environment and the generated reports are always objective, it just measures the quality facts of a given source base.
• PHP_Depend scales with growing source bases, where human code reviews will fail at some day.
• PHP_Depend allows you to identify suspect parts in a software system that should be part of a code review, without looking into the source.
• PHP_Depend also supports some fancy metrics that will become very useful, when you have reached certain level of metrics knowledge.

Conclusion

Software metrics as they are provided by tools like PHP_Depend are really useful utilities to improve the productivity of development- and quality-assurance-teams. But metrics are only indications for possible problem areas. But they are just indications and no holy grail you should follow blind.

Handbook

Installation