php_depend

In this blog post I will give you a brief introduction into the Coupling Between Objects metric, that is one of the metrics calculated by the static code analysis tool PHP_Depend.

The Coupling Between Objects or CBO metric was originally defined by Chidamber & Kemerer in their IEEE paper "A Metrics Suite for Object Oriented Design" [1]. This software metric represents the number of other types a class or interface is coupled to. The CBO metric is calculated for classes and interfaces. It counts the unique number of reference types that occur through method calls, method parameters, return types, thrown exceptions and accessed fields. But there is an exception for types that are either a subtype or supertype of the given class, because these types are not included in the calculated CBO value.

Excessive coupled classes prevent reuse of existing components and they are damaging for a modular, encapsulated software design. To improve the modularity of a software the inter coupling between different classes should be kept to a minimum. Beside reusability a high coupling has a second drawback, a class that is coupled to other classes is sensitive to changes in that classes and as a result it becomes more difficult to maintain and gets more error-prone. Additionally it is harder to test a heavly coupled class in isolation and it is harder to understand such a class. Therefore you should keep the number of dependencies at a minimum.

Thresholds

Based on their research Sahraoui, Godin and Miceli [2] suggest a maximum CBO value of 14, because higher values have negative impacts on several quality aspects of a class, which includes the maintainability, stability and understandability.

See also

Efferent Coupling:

Efferent Coupling or CE is a different name for the same metric, that is frequently used in the literatur.

Afferent Coupling:

The Afferent Coupling or CA is a metric that calculates the reverse coupling of a class.

Bibliography

[1]

http://www.iiitd.ac.in/PhD2010/papers/SW_Paper2.pdf

IEEE Transactions on Software Engineering; A Metrics Suite for Object Oriented Design; Chidamber & Kemerer, 1994

[2]

http://www.iro.umontreal.ca/~sahraouh/papers/ICSM00.pdf

Software Maintenance, 2000. Proceedings. International Conference; Can metrics help to bridge the gap between the improvement of OO design quality and its automation?; Sahraoui, Godin, Miceli; 2000

We are proud to announce release 0.10.2 of PHP_Depend. Beside two bug fixes this release implements four new software metrics:

• Efferent Coupling: The number of classes a class depends on.
• Afferent Coupling: The number of classes that depend on a class.
• Number of Public Methods: The public api/interface of a class.
• Coupling Between Objects: The coupling of a class.

A detailed CHANGELOG can be found on the project's download page and a complete, detailed description of the newly implemented software metrics in PHP_Depend's metric catalog.

This blog post will give you a brief introduction into the Class Interface Size metric, as it is calculated by the static code analysis tool PHP_Depend.

The Class Interface Size or CIS metric is measure of the public services that a class provides. This metric was orginally defined in the QMOOD model [1] by Bansiya & Davis.

The orginal version of the CIS metric was defined as the number of public methods that a class provides. Each of these methods can be seen as a service where surrounding application can send messages to or receive messages from a class.

CIS = public(NOM)

A newer variant of the CIS metric also includes the public attributes of a class, because theses properties can also be used to transport messages or information between a class and the surrounding application.

CIS = public(NOM) + public(VARS)

PHP_Depend uses the second variant and counts all public methods and attributes declared in a class to calculate its Class Interface Size metric.

This metric is a good indicator for the choosen software design. Several classes with a high CIS value are a sure sign that the design of the analyzed software prefers composition over inheritance to share common functionality between different components. So in most cases a high value is a good a sign, because composition increases the reusability and flexibility. But there are also situations where wrongly used composition of functionality leads to a design that is harder to understand and maintain.

Thresholds

It is not easy to define good thresholds for this metric, because those values heavy depend on the choosen design, e.g. inheritance or composition. But in generall we can say that is best practice to limit the public interface that can be used to alter the internal state of an object. Therefore we suggest 20 as a reference point for the upper limit.

Bibliography

[1]

http://www.ptidej.net/teaching/inf6306/fall09/notes/course4/Bansiya02-QualityModel.pdf

IEEE Transactions on Software Enginerring; Hierarchical Model for Object-Oriented Design Quality Assessment; Bansiya & Davis; 2002

Today/Yesterday we have released the bugfix version 0.9.15 and 0.9.16 of PHP_Depend. With these releases we have closed a critical bug in PHP_Depend's handling of namespaces, where identical class names in two different namespaces resulted in an endless loop, so that the php process died with a fatal error.

• Fixed #152: Endless loop bug for identical class and parent name. Fixed in svn revision #1320.
• Fixed #153: Only count those classes and interfaces that are flagged as user defined types. Fixed in subversion revision #1327.
• Implemented #154: Make execution order of analyzers reproducable. Implemented in svn revision #1331.

As always, you can get the latest PHP_Depend version from its PEAR channel: pear.pdepend.org:

mapi@arwen ~ $ pear channel-discover pear.pdepend.org
mapi@arwen ~ $ pear install pdepend/PHP_Depend-beta

Or you can fetch the sources from the subversion reposition:

mapi@arwen ~ $ svn co http://svn.pdepend.org/trunk pdepend

And additionally you can find a repository mirror on github:

mapi@arwen ~ $ git clone git://github.com/manuelpichler/pdepend.git

This blog post is in German as the mentioned article was published in German.

In der heute erschienenen Ausgabe 4.10 des PHP Magazins ist auch ein Artikel von mir enthalten, und wie sollte es wohl anders sein *Trommelwirbel*, beschäftigt der sich mit dem Thema Softwaremetriken In diesem Artikel gibt es eine sehr ausführliche Einführung in die Thematik, mit eine Reihe von praktischen Beispielen und den daraus ableitbaren Aussagen über den untersuchten Quelltext.

Über Kommentare, Anregungen und Kritik rund um den Artikel würde ich mich sehr freuen. Und sollte euch der Artikel gefallen haben, empfehle ich die Internationale PHP Conference 2010, die vom 30. Mai bis 2. Juni in Berlin stattfindet, an der ich teilnehmen und zwei Vorträge halten werden.

• Von Continuous Integration zu Continuous Deployment
• Statische Codeanalyse wirklich effektiv nutzen

This blog post is in German as the mentioned article was published in German.

In der heute erschienenen Ausgabe 4.10 des PHP Magazins ist auch ein Artikel von mir enthalten, und wie sollte es wohl anders sein *Trommelwirbel*, beschäftigt der sich mit dem Thema Softwaremetriken In diesem Artikel gibt es eine sehr ausführliche Einführung in die Thematik, mit eine Reihe von praktischen Beispielen und den daraus ableitbaren Aussagen über den untersuchten Quelltext.

Über Kommentare, Anregungen und Kritik rund um den Artikel würde ich mich sehr freuen. Und sollte euch der Artikel gefallen haben, empfehle ich die Internationale PHP Conference 2010, die vom 30. Mai bis 2. Juni in Berlin stattfindet, an der ich teilnehmen und zwei Vorträge halten werden.

• Von Continuous Integration zu Continuous Deployment
• Statische Codeanalyse wirklich effektiv nutzen

Today we have released the bugfix version 0.9.13 of PHP_Depend, the tool to measure several software metrics for your PHP application. This release fixes two critical bugs. One in the tokenizer implementation, which has modified valid code under test in such a way, that it has become invalid PHP code. The second fix is related to PHP_Depends's test code, where a missing require_once statement has caused a E_FATAL while running the test suite in PHPUnit's process isolation mode.

• Fixed #145: Incorrect require_once statement in ASTSwitchStatement source file. Fixed in svn revision #1262.
• Fixed #150: Invalid nowdoc substitution has produced broken code. Fixed in svn revision #1266.

As always, you can get the latest PHP_Depend version from its PEAR channel: pear.pdepend.org:

mapi@arwen ~ $ pear channel-discover pear.pdepend.org
mapi@arwen ~ $ pear install pdepend/PHP_Depend-beta

Or you can fetch the sources from the subversion reposition:

mapi@arwen ~ $ svn co http://svn.pdepend.org/trunk pdepend

And additionally you can find a repository mirror on github:

mapi@arwen ~ $ git clone git://github.com/manuelpichler/pdepend.git

As many of you may already have noticed, there will be a big change in my career as a professional software engineer and architect this summer. Together with Kore and Toby I am in the process of founding a company. The focus of this company will be on services all around the whole quality life cycle in PHP projects.

Under the hood of our company we will also offer support, trainings and consulting for several quality assurance tools, like pdepend, phpmd and phpUnderControl. For you, this opens a great opportunity. You can use the tools and the documentation, as well as participate in the community, as usual. But from now on you can also purchase professional support, if you get stuck or need general assitance. And when you miss a feature or need an individual extension for one of these tools, don't hesitate to contact us.

I am really excited what cool things will happen in the next couple of years and I am looking forward to cowork with professionals like Toby and Kore.

To finalize the little marketing for the company and its services I would appreciate to meet you, your colleagues and your compmany, to give presentations or into-depth trainings on one of the tools or on quality assurance in general.

I am proud to announce the 0.9.12 release of PHP_Depend. PHP_Depend is a low level static code analysis tool. It takes the given source and calculates several software metrics for the code. This data can be used by software-developers, architects and designers to control the quality of a software-product without time consuming code audits.

This new release of PHP_Depend has done a great step into the direction of a token free PHP_Depend version. This means future versions of PHP_Depend will work without the need to traverse linear token streams up and down, to measure metrics. Instead PHP_Depend will rely on it's internal abstract syntax tree, that represents the logical structure of the analyzed source code. With this solution it will be possible to implement several new features that will make PHP_Depend more useful, for example static callgraph analysis.

• Implemented #97: Replace current token approach in CCN- and NPath-Analyzer with AST-Nodes. Implemented in svn revision #1248.
• Implemented #125: PHP_Depend silently parses list statements. Fixed in svn revision #1223. Thanks to Joey Mazzarelli for providing this patch.
• Implemented #126: Generate reproducable node identifiers instead of random numbers. Implemented in svn revision #1244.
• Fixed #128: Variable variables in foreach statement cause an exception. Fixed in svn revision #1237.
• Fixed #133: Fatal error: Maximum function nesting level of '100' reached, aborting! in /usr/share/pear/PHP/Depend/Util/Log.php on line 109. Fixed in svn revision #1257.
• Fixed #134: ASTReturnStatement is not derived from ASTStatement. Fixed in svn revision #1250.
• Fixed #135: Several Statement classes do not inherit ASTStatement. Fixed in svn revision #1255.

As always, you can get the latest PHP_Depend version from its PEAR channel: pear.pdepend.org:

mapi@arwen ~ $ pear channel-discover pear.pdepend.org
mapi@arwen ~ $ pear install pdepend/PHP_Depend-beta

Or you can fetch the sources from the subversion reposition:

mapi@arwen ~ $ svn co http://svn.pdepend.org/trunk pdepend

And additionally you can find a repository mirror on github:

mapi@arwen ~ $ git clone git://github.com/manuelpichler/pdepend.git

I have just released version 0.9.11 of PHP_Depend. It contains a few bug fixes and improvements for PHP_Depend.

• Fixed #118: Calculation of the Number Of Overwritten Methods is wrong. Fixed in svn revision #1112.
• Fixed #119: Three test cases fail for all PHP versions prior to 5.3. Fixed in svn revision #1114.
• Implemented #121: Parse arguments of the ASTForeachStatement. Implemented in svn revision #1115.
• Critical issue in PHP_Depend's temporary data cache fixed. This bug only occured when running several instances of PHP_Depend in parallel. In this setup the used cache key spl_object_hash() has caused a corrupted cache, because different php process instances have written different data to the same cache file.

As always, you can get the latest PHP_Depend version from its PEAR channel: pear.pdepend.org:

  mapi@arwen ~ $ pear channel-discover pear.pdepend.org
  mapi@arwen ~ $ pear install pdepend/PHP_Depend-beta

Or you can fetch the sources from the subversion reposition:

  mapi@arwen ~ $ svn co http://svn.pdepend.org/branches/0.9.0/

And additionally you can find a repository mirror on github:

  mapi@arwen ~ $ git clone git://github.com/manuelpichler/pdepend.git

I have just released the bug fix version 0.9.10 of PHP_Depend. This release contains several bug fixes and improvements for PHP_Depend.

• Implemented #72__: Add NOAM, NOOM and NOCC metrics. Implemented in svn revision #1084.
• Implemented #74: Make CRAP-index available. Implemented in svn revision #1063.
• Implemented #105: Support for deep search implement. Implemented in svn revision #1078.
• Fixed #106: Filter algorithm is broken for namespaced internal classes. Fixed in svn revision #1039.
• Fixed #110: Duplicate "coupling" directory in test code. Fixed in svn revision #1032.
• Fixed #111: Dynamic Strings are treated as literal strings. Fixed in svn revision #1037.
• Fixed #114: Parsing error caused by complex string expressions fixed. Fixed in svn revision #1068.
• Fixed #115: Summary and PHPUnit Report lists unknown classes. Fixed in svn revision #1101.
• Fixed #116: Returns reference results in parsing error. Fixed in svn revision #1090.
• Performance intensive calculation result cached.
• Test code restructured and improved.
• Concurrency issue for parallel running pdepend instances fixed.

As always, you can get the latest PHP_Depend version from its PEAR channel: pear.pdepend.org:

  mapi@arwen ~ $ pear channel-discover pear.pdepend.org
  mapi@arwen ~ $ pear install pdepend/PHP_Depend-beta

Or you can fetch the sources from the subversion reposition:

  mapi@arwen ~ $ svn co http://svn.pdepend.org/branches/0.9.0/

And additionally you can find a repository mirror on github:

  mapi@arwen ~ $ git clone git://github.com/manuelpichler/pdepend.git

Today I have released version 0.2.0 of the PHP Mess Detector or short PHPMD. PHPMD is a simple, customizable and user friendly frontend application for PHP_Depend. It takes the raw metrics measured by PHP_Depend, compares them with appropriate thresholds and generates a report that lists those software artifacts with potential problems. Such a report can be taken as a basis for human code audits or you can use it as input for an automated build/reporting tool.

Most concepts behind PHPMD are based on those of the well known Java Tool PMD. It uses so called rule set files to organize different sets of rules. There are two purposes that are accomplished by these xml files. The first is to create custom sets of rules which fulfills the projects requirements. The second purpose is the configuration of each rule with thresholds, warning messages and other things. The format of these files is totally borrowed from PMD, so that the reuse existing rule sets in multi language environments should be easy. At the moment PHPMD has two build-in rule sets. One that detects software artifacts with high code size, and the second one detects unused code in your software.

Now lets start with a small How to use it. PHPMD can be called from the command line by typing phpmd, which prints a general help text.

mapi@arwen ~ $ phpmd 
Mandatory arguments:
1) A php source code filename or directory
2) A report format
3) A ruleset filename or a comma-separated string of ...

Optional arguments that may be put after the mandato...
--minimumpriority: rule priority threshold; rules with ...
--reportfile: send report output to a file; default to ...
--extensions: comma-separated string of valid source ...
--ignore: comma-separated string of patterns that are ...

Now let's call PHPMD on its own source, with a simple text report on STDOUT and the codesize ruleset:

mapi@arwen ~ $ phpmd ~/phpmd/source text codesize

/home/mapi/phpmd/source/PHP/PMD/RuleSetFactory.php:66 \
  This class has too many methods, consider refactoring it.
/home/mapi/phpmd/source/PHP/PMD/RuleSetFactory.php:267 \
  The method _parseSingleRuleNode() has a Cyclomatic \
  Complexity of 11.
/home/mapi/phpmd/source/PHP/PMD/RuleSetFactory.php:326 \
  The method _parseRuleReferenceNode() has a Cyclomatic \
  Complexity of 10.

The --reportfile option can be used, to redirect the report output into a file. So let us repeat the previous example that writes the report into a file, additionally uses the unusedcode rule and changes the format from text to xml.

mapi@arwen ~ $ phpmd ~/phpmd/source xml codesize,unusedcode \
  --reportfile ~/pmd.xml
mapi@arwen ~ $ cat ~/pmd.xml 
<?xml version="1.0" encoding="UTF-8" ?>
<pmd version="@package_version@" timestamp="...">
  <file name=".../source/PHP/PMD/RuleSetFactory.php">
    <violation beginline="66" endline="417" rule="TooManyMet ...>
      This class has too many methods, consider refactoring it.
    </violation>
    <violation beginline="267" endline="315" rule="Cyclomati ...>
      Method _parseSingleRule() has a Cyclomatic Complexity of 11.
    </violation>
    <violation beginline="326" endline="367" rule="Cyclomati ...>
      Method _parseRuleReference() has a Cyclomatic Complexity of 10.
    </violation>
  </file>
</pmd>

This xml file is compatible with those files generated by PMD and PHPUnit's deprecated --log-pmd option. So that it should be no problem to use this files in existing environments like Hudson, CruiseControl or Sonar.

Currently PHPMD supports the following three different report formats: Text, HTML and XML. And it has the build-in rule sets: codesize and unusedcode.

You can get the latest PHPMD version from its PEAR channel: pear.phpmd.org

mapi@arwen ~ $ pear channel-discover pear.pdepend.org
mapi@arwen ~ $ pear channel-discover pear.phpmd.org
mapi@arwen ~ $ pear install --alldeps phpmd/PHP_PMD-alpha

I have just released the bug fix version 0.9.9 of PHP_Depend.

• Fixed #108: Parser doesn't set start/end line/column on variables, fixed in svn revision #1015.
• Implemented #104: Add isStatic() method on ASTMemberPrimaryPrefix node, implemented in svn revision #1013.

You can get the latest PHP_Depend version from its PEAR channel: pear.pdepend.org

mapi@arwen ~ $ pear channel-discover pear.pdepend.org
mapi@arwen ~ $ pear install pdepend/PHP_Depend-beta

Today I released PHP_Depend 0.9.8, which contains many bug fixes and improvements. This release will be the base version for a new tool called PHPMD. PHPMD is a frontend that reports critical and suspect software artifacts in a project, based on the metrics measured with PHP_Depend. It aims to be a PHP equivalent to the well known java tool PMD.

• Closed #93: Implement an assignment expression, Implemented in svn revision #992.
• Fixed #94: Parser throws exception for closures that return by reference, fixed in svn revision #962.
• Fixed #98: Functions with an invalid signature result in an inconsistent object graph, fixed in svn revision #986.
• Fixed #102: Namespace keyword in type-hint is broken, fixed in svn revision #1010.
• Fixed #103: The parser does not handle all strings as parameter default value correct, fixed in svn revision #1009.

You can get the latest PHP_Depend version from its PEAR channel: pear.pdepend.org

mapi@arwen ~ $ pear channel-discover pear.pdepend.org
mapi@arwen ~ $ pear install pdepend/PHP_Depend-beta

Today Fabien Potencier announced the first relase of the PEAR Channel server Pirum. The great benefit of this Channel server is that it provides a simple shell script to publish new PEAR package releases, a feature that I missed in the previously used Chiara PEAR Server. Pirum will make it really easy to publish new package versions through a simple build script

The setup was quick done, following the instructions on the pirum website, and importing the existing package files worked like a charm. The only problem I encountered was that both channel server implementations use a different directory structure. Pirum stores all the XML descriptors under a directory named /rest, while my Chiara Server installation has used /Chiara_PEAR_Server_REST, so that a first call to pear upgrade resulted in the following error:

manu@arwen ~ $ pear upgrade
Error getting channel info from pear.pdepend.org: \
File http://pear.pdepend.org:80/Chiara_PEAR_Server_REST/p/packages.xml \
not valid (received: HTTP/1.1 404 Not Found)

But a simple 301 redirect makes this software transition transparent for the PHP_Depend users. So when you will also switch to Pirum you should keep this in mind and test your channel server with an existing/configured local pear installation.

Finally, thanks to Fabien for this nitty-gritty tool, which will speed up the deployment process of PEAR packages, at least for me.