PHPDeps

Table of Contents

• About
• Install
• Why care?
• Approach
• Basic usage
• Example
• Exit codes
• Config
• Config example
• Commands and options

About

PHPDeps is a simple tool to detect circular dependencies in your modules, whatever you consider as a module or package.

Module is an organized unit of code, which is supposed to be treated as single entity. By grouping classes and functions into modules we can reason about the design at a higher level of abstraction.

Install

PHPDeps is available via composer:

composer require --dev koriit/phpdeps

Please, note that PHPDeps is used during the development. It’s not a part of your application, hence --dev.

Why care?

This is a general programming problem. If this subject is new to you, or you just need a refresher here are some quick references:

1. Why Cyclic Dependencies are Bad

2. What is circular dependency and why is it bad?

3. Circular dependency

4. Acyclic dependencies principle

5. The Principles of OOD (The Acyclic Dependencies Principle part; in the end, most of the writers refer to this piece of literature)

Approach

TL;DR

If you are using PSR-4 and importing all classes and function via use then you are fine.

PHPDeps detects module usage by reading use section of your PHP files. This means that PHPDeps requires namespaces to be present.

PHPDeps assumes that all classes and functions belonging to a single module have the same namespace prefix in their fully qualified name.

For example, if we tell PHPDeps that SomeModule has namespace of ACME\Lib\Modules\SomeModule and PHPDeps analyzes a following file which belongs to OtherModule:

<?php
namespace ACME\Lib\Modules\OtherModule;

use ACME\Lib\Modules\SomeModule\Exceptions\ObjectNotFound;
// ...

Then PHPDeps notices that OtherModule depends on SomeModule.

Once all modules are analyzed, PHPDeps creates a dependency graph and looks for any cycles in it.

Basic usage

If you are all configured and set then just execute:

vendor/bin/phpdeps

If your configuration file is not named phpdeps.xml then you can pass it as --config option:

vendor/bin/phpdeps --config=myPHPDepsConfig.xml

It’s suggested to add phpdeps call to scripts section in your composer.json:

  "scripts": {
    "dependencies": "phpdeps"
  }

You can also run it alongside your tests:

  "scripts": {
    "test": ["phpunit", "phpdeps"]
  }

Example

Let’s consider a simplified structure of PHPDeps itself:

/src/PHPDeps
|-- ExtCodes.php
|-- PHPDepsApplication.php
|-- /Commands/
|-- /Config/
|-- /Modules/
|-- /Helpers/

First, you need to prepare a configuration file that will allow PHPDeps to find your modules:

phpdeps.xml

<?xml version="1.0" encoding="UTF-8"?>
<PHPDeps xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:noNamespaceSchemaLocation="vendor/koriit/phpdeps/phpdeps.xsd">

    <Modules> <!--(1)-->
        <Module>
            <Name>PHPDepsApplication</Name> <!--(2)-->
            <Namespace>Koriit\PHPDeps\PHPDepsApplication</Namespace> <!--(3)-->
            <Path>./src/PHPDeps/PHPDepsApplication.php</Path> <!--(4)-->
        </Module>
    </Modules>

    <Detectors> <!--(5)-->
        <ModuleDetector>
            <Namespace>Koriit\PHPDeps</Namespace> <!--(6)-->
            <Path>./src/PHPDeps</Path> <!--(7)-->
        </ModuleDetector>
    </Detectors>

</PHPDeps>

1. First option is to directly define your modules.

2. Each module needs a name, but currently this is only used for displaying purposes.

3. Each module also needs a namespace prefix, this is used to check whether any other module depends on it. If module is a file then this needs to be fully qualified name of that module.

4. Module path allows PHPDeps to find and analyze your module, this can be either filepath or dirpath.

5. Second option is to define a module detector, right now PHPDeps supports detection of only dir based modules.

6. Namespace prefix, directory name of found modules are appended to this to create actual module namespaces.

7. Directory where modules are to be searched for.

Once you have a configuration ready, you can execute:

vendor/bin/phpdeps

If everything is all right you get nice OK message:

[OK] There are no circular dependencies in your modules!

If something is amiss, you get:

[WARNING] There are circular dependencies in your modules!

In total there are 4 dependency cycles in your modules.

1. Commands -> Modules -> Commands
----------------------------------

2. Commands -> Config -> Modules -> Commands
--------------------------------------------

3. Commands -> Helpers -> Modules -> Commands
---------------------------------------------

4. Commands -> Helpers -> Config -> Modules -> Commands
-------------------------------------------------------

Please, note that this example was generated by adding just one dependency to Commands module in Modules module.

At the moment PHPDeps does not provide any additional help in resolving the circular dependencies problem.

Exit codes

Code	Name	Description
0	OK	Application finished successfully and no issues detected
1	UNEXPECTED_ERROR	Application was aborted because of an error
3	CIRCULAR_DEPENDENCIES_EXIST	Application finished successfully but dependency cycle has been detected
255	STATUS_OUT_OF_RANGE	Returned status code was out of range

Config

Configuration is a simple XML file. Provided XSD allows for code completion and easy validation. Currently, configuration uses simple format consisting of only XML tags and no attributes

• <PHPDeps> - Configuration root element.

  • <Modules> - Grouping tag for all kinds of module definitions.

    • <Module> - Defines and describes a single module.

      • <Name> - Module name, used for display purposes.

      • <Namespace> - Namespace prefix, to check whether any other module depends on it. If module is a file then this needs to be fully qualified name of that module.

      • <Path> - Module path allows PHPDeps to find and analyze your module, this can be either filepath or dirpath.

  • <Detectors> - Grouping tag for all kinds of detector definitions.

    • <ModuleDetector> - Defines and describes a single basic module detector.

      • <Namespace> - Namespace prefix, directory name of found modules are appended to this to create actual module namespaces.

      • <Path> - Directory where modules are to be searched for.

Config example

phpdeps.xml

<?xml version="1.0" encoding="UTF-8"?>
<PHPDeps xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:noNamespaceSchemaLocation="vendor/koriit/phpdeps/phpdeps.xsd">

    <Modules>
        <Module>
            <Name>PHPDepsApplication</Name>
            <Namespace>Koriit\PHPDeps\PHPDepsApplication</Namespace>
            <Path>./src/PHPDeps/PHPDepsApplication.php</Path>
        </Module>
    </Modules>

    <Detectors>
        <ModuleDetector>
            <Namespace>Koriit\PHPDeps</Namespace>
            <Path>./src/PHPDeps</Path>
        </ModuleDetector>
    </Detectors>

</PHPDeps>

Commands and options

Please, refer to built-in help command.