PHP Coding Guidelines & Best Practices

PHP Coding Guidelines & Best Practices

Coding Standards are an important factor for achieving a high code quality. A common visual style, naming conventions and other technical settings allow us to produce a homogenous code which is easy to read and maintain. However, not all important factors can be covered by rules and coding standards. Equally important is the style in which certain problems are solved programmatically - it's the personality and experience of the individual developer which shines through and ultimately makes the difference between technically okay code or a well considered, mature solution.

These guidelines try to cover both, the technical standards as well as giving incentives for a common development style. These guidelines must be followed by everyone who creates code for the TYPO3 Flow core. Because Neos is based on TYPO3 Flow, it follows the same principles - therefore, whenever we mention TYPO3 Flow in the following sections, we equally refer to Neos. We hope that you feel encouraged to follow these guidelines as well when creating your own packages and TYPO3 Flow based applications.

CGL on One Page

The Coding Guidelines on One Page

The most important parts of our Coding Guidelines in a one page document you can print out and hang on your wall for easy reference. Does it get any easier than that?

Code Formatting and Layout aka "beautiful code"

The visual style of programming code is very important. In the TYPO3 project we want many programmers to contribute, but in the same style. This will help us to:

• Easily read/understand each others code and consequently easily spot security problems or optimization opportunities
• It is a signal about consistency and cleanliness, which is a motivating factor for programmers striving for excellence

Some people may object to the visual guidelines since everyone has his own habits. You will have to overcome that in the case of TYPO3 Flow; the visual guidelines must be followed along with coding guidelines for security. We want all contributions to the project to be as similar in style and as secure as possible.

General considerations

• Almost every PHP file in TYPO3 Flow contains exactly one class and does not output anything if it is called directly. Therefore you start your file with a <?php tag and end it with the closing ?>.
• Every file must contain a header stating namespace and licensing information
  • Declare your namespace.
  • The copyright header itself must not start with /**, as this may confuse documentation generators!

The TYPO3 Flow standard file header:

<?php
namespace YourCompany\Package\Stuff\Here;

/*                                                                        *
 * This script belongs to the TYPO3 Flow package "Package".               *
 *                                                                        *
 * It is free software; you can redistribute it and/or modify it under    *
 * the terms of the GNU Lesser General Public License, either version 3   *
 * of the License, or (at your option) any later version.                 *
 *                                                                        *
 * The TYPO3 project - inspiring people to share!                         *
 *                                                                        */

• Code lines are of arbitrary length, no strict limitations to 80 characters or something similar (wake up, graphical displays have been available for decades now...). But feel free to break lines for better readability if you think it makes sense!
• Lines end with a newline a.k.a chr(10) - UNIX style
• Files must be encoded in UTF-8 without byte order mark (BOM)

Make sure you use the correct license and mention the correct package in the header, we have some some boilerplate text.

Indentation and line formatting

Indentation is done with tabs - and not spaces! The beginning of a line is the only place where tabs are used, in all other places use spaces. Always trim whitespace off the end of a line.

Here's a code snippet which shows the correct usage of tabs and spaces.

Correct use of tabs and spaces:

/**
 * Returns the name of the currently set context.
 *
 * @return string Name of the current context
 * @author Your Name <your@email.here>
 */
public function getContextName() {
  return $this->contextName;
}

There seem to be very passionate opinions about whether TABs or spaces should be used for indentation of code blocks in the scripts. If you'd like to read more about this religious discussion, you find some nice arguments in the Joels on Software forum.

Naming

Naming is a repeatedly undervalued factor in the art of software development. Although everybody seems to agree on that nice names are a nice thing to have, most developers choose cryptic abbreviations in the end (to save some typing). Beware that we TYPO3 core developers are very passionate about naming (some people call it fanatic, well ...). In our opinion spending 15 minutes (or more ...) just to find a good name for a method is well spent time! There are zillions of reasons for using proper names and in the end they all lead to better readable, manageable, stable and secure code.

As a general note, english words (or abbreviations if necessary) must be used for all class names, method names, comments, variables names, database table and field names. The consensus is that english is much better to read for the most of us, compared to other languages.

When using abbreviations or acronyms remember to make them camel-cased as needed, no all-uppercase stuff. Admittedly there are a few places where we violate that rule willingly (TYPO3 – will not change) and historically.

Vendor namespaces

The base for namespaces as well as package keys is the vendor namespace. Since Flow is part of the TYPO3 project, the core team decided to choose "TYPO3" as our vendor namespace. The Object Manager for example is known under the class nameTYPO3\Flow\Object\ObjectManager. In our examples you will find the Acme vendor namespace.

Why do we use vendor namespaces? This has two great benefits: first of all we don't need a central package key registry (like the one we have for TYPO3 4.x extensions) and secondly, it allows anyone to seamlessly integrate third-party packages, such as Symfony2 components and Zend Framework components or virtually any other PHP 5.3 based library.

Think about your own vendor namespace for a few minutes. It will stay with you for a long time.

Package names

All package names start with an uppercase character and usually are written in UpperCamelCase. In order to avoid problems with different filesystems, only the characters a-z, A-Z, 0-9 and the dash sign "-" are allowed for package names – don't use special characters.

The full package key is then built by combining the vendor namespace and the package, like TYPO3.Fluid or Acme.Demo.

Namespace and Class names

• Only the characters a-z, A-Z and 0-9 are allowed for namespace and class names.
• Namespaces are usually written in UpperCamelCase but variations are allowed for well established names and abbreviations.
• Class names are always written in UpperCamelCase.
• The unqualified class name must be meant literally even without the namespace.
• The main purpose of namespaces is categorization and ordering
• Class names must be nouns, never adjectives.
• The name of abstract classes must start with the word "Abstract", class names of aspects must end with the word "Aspect".

Incorrect naming of namespaces and classes

Fully qualified class name	Unqualified name	Remarks
\TYPO3\Flow\Session\Php	Php	The class is not a representation of PHP
\TYPO3\Flow\Cache\Backend\File	File	The class doesn't represent a file!
\TYPO3\Flow\Session\Interface	Interface	Not allowed, "Interface" is a reserved keyword
\TYPO3\Foo\Controller\Default	Default	Not allowed, "Default" is a reserved keyword
\TYPO3\Flow\Object\Manager	Manager	Just "Manager" is too fuzzy

Correct naming of namespaces and classes

Fully qualified class name	Unqualified name	Remarks
\TYPO3\Flow\Session\PhpSession	PHPSession	That's a PHP Session
\TYPO3\Flow\Cache\Backend\FileBackend	FileBackend	A File Backend
\TYPO3\Flow\Session\SessionInterface	SessionInterface	Interface for a session
\TYPO3\Foo\Controller\StandardController	StandardController	The standard controller
\TYPO3\Flow\Object\ObjectManager	ObjectController	"ObjectManager" is clearer

Edge cases in naming of namespaces and classes

Fully qualified class name	Unqualified name	Remarks
\TYPO3\Flow\Mvc\ControllerInterface	ControllerInterface	Consequently the interface belongs to all the controllers in the Controller sub namespace
\TYPO3\Flow\Mvc\Controller\ControllerInterface		Better
\TYPO3\Flow\Cache\AbstractBackend	AbstractBackend	Same here: In reality this class belongs to the backends
\TYPO3\Flow\Cache\Backend\AbstractBackend		Better

Note

When specifying class names to PHP, always reference the global namespace inside namespaced code by using a leading backslash. When referencing a class name inside a string (e.g. given to the get-Method of the ObjectManager, in pointcut expressions or in YAML files), never use a leading backslash. This follows the native PHP notion of names in strings always being seen as fully qualified.

Interface names

Only the characters a-z, A-Z and 0-9 are allowed for interface names – don't use special characters.

All interface names are written in UpperCamelCase. Interface names must be adjectives or nouns and have the Interface suffix. A few examples follow:

• \TYPO3\Flow\Object\ObjectInterface
• \TYPO3\Flow\Object\ObjectManagerInterface
• \MyCompany\MyPackage\MyObject\MySubObjectInterface
• \MyCompany\MyPackage\MyObject\MyHtmlParserInterface

Exception names

Exception naming basically follows the rules for naming classes. There are two possible types of exceptions: generic exceptions and specific exceptions. Generic exceptions should be named "Exception" preceded by their namespace. Specific exceptions should reside in their own sub-namespace end with the word Exception.

• \TYPO3\Flow\Object\Exception
• \TYPO3\Flow\Object\Exception\InvalidClassNameException
• \MyCompany\MyPackage\MyObject\Exception
• \MyCompany\MyPackage\MyObject\Exception\OutOfCoffeeException

Method names

All method names are written in lowerCamelCase. In order to avoid problems with different filesystems, only the characters a-z, A-Z and 0-9 are allowed for method names – don't use special characters.

Make method names descriptive, but keep them concise at the same time. Constructors must always be called __construct(), never use the class name as a method name.

• myMethod()
• someNiceMethodName()
• betterWriteLongMethodNamesThanNamesNobodyUnderstands()
• singYmcaLoudly()
• __construct()

Variable names

Variable names are written in lowerCamelCase and should be

• self-explanatory
• not shortened beyond recognition, but rather longer if it makes their meaning clearer

The following example shows two variables with the same meaning but different naming. You'll surely agree the longer versions are better (don't you ...?).

Correct naming of variables

• $singletonObjectsRegistry
• $argumentsArray
• $aLotOfHTMLCode

Incorrect naming of variables

• $sObjRgstry
• $argArr
• $cx

As a special exception you may use variable names like $i, $j and $k for numeric indexes in for loops if it's clear what they mean on the first sight. But even then you should want to avoid them.

Constant names

All constant names are written in UPPERCASE. This includes TRUE, FALSE and NULL. Words can be separated by underscores - you can also use the underscore to group constants thematically:

• STUFF_LEVEL
• COOLNESS_FACTOR
• PATTERN_MATCH_EMAILADDRESS
• PATTERN_MATCH_VALIDHTMLTAGS

It is, by the way, a good idea to use constants for defining regular expression patterns (as seen above) instead of defining them somewhere in your code.

Filenames

These are the rules for naming files:

• All filenames are UpperCamelCase.
• Class and interface files are named according to the class or interface they represent
• Each file must contain only one class or interface
• Names of files containing code for unit tests must be the same as the class which is tested, appended with "Test.php".
• Files are placed in a directory structure representing the namespace structure.

File naming in TYPO3 Flow

TYPO3.TemplateEngine/Classes/TYPO3/TemplateEngine/TemplateEngineInterface.php

Contains the interface \TYPO3\TemplateEngine\TemplateEngineInterface which is part of the packageTYPO3.TemplateEngine

TYPO3.Flow/Classes/TYPO3/Flow/Error/RuntimeException.php

Contains the \TYPO3\Flow\Error\RuntimeException being a part of the package TYPO3.Flow

Acme.DataAccess/Classes/Acme/DataAccess/Manager.php

Contains class \Acme\DataAccess\Manager which is part of the package Acme.DataAccess

TYPO3.Flow/Tests/Unit/Package/PackageManagerTest.php

Contains the class \TYPO3\Flow\\Tests\Unit\Package\PackageManagerTest which is a PHPUnit testcase forPackage\PackageManager.

PHP code formatting

Inline comments

Inline comments must be indented one level more than surrounding source code. For documentation comments see Source Code Documentation.

Strings

In general, we use single quotes to enclose literal strings:

$vision = 'Inspiring people to share';

If you'd like to insert values from variables, concatenate strings:

$message = 'Hey ' . $name . ', you look ' . $look . ' today!';

A space must be inserted before and after the dot for better readability:

$vision = 'Inspiring people ' . 'to share.';

You may break a string into multiple lines if you use the dot operator. You'll have to indent each following line to mark them as part of the value assignment:

$vision = 'Inspiring' .
  'people ' .
  'to ' .
  'share';

Arrays

Classes

Functions and methods

if statements

• There needs to be one space between the if keyword and the opening brace "(" of the test expression
• After the closing brace ")" of the test expression follows one space before the curly brace "{"
• else and elseif are on the same line as their corresponding curly braces

if statements:

if ($something || $somethingElse) {
  doThis();
} else {
  doSomethingElse();
}

if (weHaveALotOfCriteria() === TRUE
  && notEverythingFitsIntoOneLine() === TRUE
  || youJustTendToLikeIt() === TRUE) {
     doThis();

} else {
  ...
}

switch statements

• There needs to be one space between the if keyword and the opening brace "(" of the test expression
• After the closing brace ")" of the test expression follows one space before the curly brace "{"
• break is indented to the same level as case keywords

switch statements:

switch ($something) {
  case FOO:
     $this->handleFoo();
  break;
  case BAR:
     $this->handleBar();
  break;
  default:
     $this->handleDefault();
}

Development Process

Test-Driven Development

In a nutshell: before coding a feature or fixing a bug, write an unit test.

Whatever you do: before committing changes to the repository, run all unit tests to make sure nothing is broken!

Commit Messages

To have a clear and focused history of code changes is greatly helped by using a consistent way of writing commit messages. Because of this and to help with (partly) automated generation of change logs for each release we have defined a fixed syntax for commit messages that is to be used.

Tip

Never commit without a commit message explaining the commit!

The syntax is as follows:

• One line with a short summary, no full stop at the end. If the change breaks things on the user side, start the line with [!!!]. This indicates a breaking change that needs human action when updating.
  Then followed by one or more of the following codes:

  [FEATURE]

  A feature change. Most likely it will be an added feature, but it could also be removed. For additions there should be a corresponding ticket in the issue tracker.

  [BUGFIX]

  A fix for a bug. There should be a ticket corresponding to this in the issue tracker as well as a new) unit test for the fix.

  [API]

  An API change, that is methods have been added or removed; method signatures or return types have changed. This only refers to the public API, i.e. methods tagged with @api.

  [CONFIGURATION]

  Some configuration change. That could be a changed default value, a new setting or the removal of some setting that used to exist.

  [TASK]

  Anything not covered by the above categories, e.g. coding style cleanup. Usually only used if there's no corresponding ticket.

• Then follows (after a blank line) a custom message explaining what was done. It should be written in a style that serves well for a change log read by users. In case of breaking changes give a hint on what needs to be changed by the user.
• If corresponding tickets exist, mention the ticket numbers using footer lines after another blank line and use the following actions:

  Fixes: #<number>

  If the change fixes a bug.

  Resolves: #<number>

  If the change resolves a feature request or task.

  Related: #<number>

  If the change relates to an issue but does not resolve or fix it.

• Fixes may be targeted at not only the master branch (i.e. the next major/point release), but also for a point release in an older branch. Thus a Releases footer must address the target branches.

A commit messages following the rules...:

[TASK] Short (50 chars or less) summary of changes

More detailed explanatory text, if necessary.  Wrap it to about 72
characters or so.  In some contexts, the first line is treated as the
subject of an email and the rest of the text as the body.  The blank
line separating the summary from the body is critical (unless you omit
the body entirely); tools like rebase can get confused if you run the
two together.

Write your commit message in the present tense: "Fix bug" and not "Fixed
bug."  This convention matches up with commit messages generated by
commands like git merge and git revert.

Further paragraphs come after blank lines.

* Bullet points are okay, too
* An asterisk is used for the bullet, it can be preceded by a single
  space. This format is rendered correctly by Forge (redmine)
* Use a hanging indent

Resolves: #123
Resolves: #456
Related: #789
Releases: 1.0, 1.1

Source Code Documentation

All code must be documented with inline comments. The syntax is similar to that known from the Java programming language (JavaDoc). This way code documentation can automatically be generated using PHP_UML.

Documentation Blocks

A file contains different documentation blocks, relating to the class in the file and the members of the class. A documentation block is always used for the entity it precedes.

Class documentation

Classes have their own documentation block describing the classes purpose.

Standard documentation block:

/**
 * First sentence is short description. Then you can write more, just as you like
 *
 * Here may follow some detailed description about what the class is for.
 *
 * Paragraphs are separated by an empty line.
 */
class SomeClass {
 ...
}

Additional tags or annotations, such as @see or @Flow\Aspect, can be added as needed.

Documenting variables, constants, includes

Properties of a class should be documented as well. We use the short version for documenting them.

Standard variable documentation block:

/**
 * A short description, very much recommended
 * @var string
 */
protected $title = 'Untitled';

Method documentation

For a method, at least all parameters and the return value must be documented. The @access tag must not be used as it makes no sense (we're using PHP 5 for a reason, don't we?)

Standard method documentation block:

/**
 * A description for this method
 *
 * Paragraphs are separated by an empty line.
 *
 * @param \TYPO3\Blog\Domain\Model\Post $post A post
 * @param string $someString This parameter should contain some string
 * @return void
 */
public function addStringToPost(\TYPO3\Blog\Domain\Model\Post $post, $someString) {
 ...
}

A special note about the @param tags: The parameter type and name are separated by one space, not aligned. Do not put a colon after the parameter name. Always document the return type, even if it is void - that way it is clearly visible it hasn't just been forgotten (only constructors never have a @return annotation!).

Testcase documentation

Testcases need to be marked as being a test and can have some more annotations.

Standard testcase documentation block:

/**
 * @test
 */
public function fooReturnsBarForQuux() {
 ...
}

Defining the Public API

Not all methods with a public visibility are necessarily part of the intended public API of a project. For TYPO3 Flow, only the methods explicitly defined as part of the public API will be kept stable and are intended for use by developers using TYPO3 Flow. Also the API documentation we produce will only cover the public API.

To mark a method as part of the public API, include an @api annotation for it in the docblock.

Defining the public API:

/**
 * This method is part of the public API.
 *
 * @return void
 * @api
 */
public function fooBar() {
 ...
}

Tip

When something in a class or an interface is annotated with @api make sure to also annotate the class or interface itself! Otherwise it will be ignored completely when official API documentation is rendered!

Overview of Documentation Annotations

There are not only documentation annotations that can be used. In TYPO3 Flow annotations are also used in the MVC component, for defining aspects and advices for the AOP framework as well as for giving instructions to the Persistence framework. See the individual chapters for information on their purpose and use.

Here is a list of annotations used within the project. They are grouped by use case and the order given here should be kept for the sake of consistency.

Interface Documentation

• @api
• @since
• @deprecated

Class Documentation

• @api
• @since
• @deprecated
• @FlowEntity
• @FlowValueObject
• @FlowScope
• @FlowAspect

Property Documentation

• @var
• @FlowIntroduce
• @FlowIdentity
• @FlowTransient
• @FlowLazy
• @api
• @since
• @deprecated

Constructor Documentation

• @param
• @throws
• @api
• @since
• @deprecated

Method Documentation

• @param
• @return
• @throws
• @FlowValidate
• @FlowIgnoreValidation
• @FlowSignal
• @api
• @since
• @deprecated
• @FlowPointcut
• @FlowAfterReturning
• @FlowAfterThrowing
• @FlowAround
• @FlowBefore

Testcase Documentation

• @test
• @dataProvider
• @expectedException

Tip

Additional annotations (more or less only the @todo and @see come to mind here), should be placed after all other annotations.

Best Practices

TYPO3 Flow

This section gives you an overview of TYPO3 Flow's coding rules and best practices.

Error Handling and Exceptions

TYPO3 Flow makes use of a hierarchy for its exception classes. The general rule is to throw preferably specific exceptions and usually let them bubble up until a place where more general exceptions are caught. Consider the following example:

Some method tried to retrieve an object from the object manager. However, instead of providing a string containing the object name, the method passed an object (of course not on purpose - something went wrong). The object manager now throws anInvalidObjectName exception. In order to catch this exception you can, of course, catch it specifically - or only consider a more general Object exception (or an even more general Flow exception). This all works because we have the following hierarchy:

+ \TYPO3\Flow\Exception
+ \TYPO3\Flow\Object\Exception
+ \TYPO3\Flow\Object\Exception\InvalidObjectNameException

Throwing an exception

When throwing an exception, make sure to provide a clear error message and an error code being the unix timestamp of when you write the ``throw`` statement. That error code must be unique, so watch out when doing copy and paste!

For every exception there should be a page on the TYPO3 wiki, as exception messages link to that page, identified by the error code (unix timestamp).

Unit Testing

Some notes for a start:

• Never use the object manager or factory in unit tests! If they are needed, mock them.
• Avoid tests for the scope of an object. Those tests test the object factory, rather then the test target. Such a test should be done by checking for the presence of an expected @scope annotation – eventually we will find an elegant way for this.

Cross Platform Coding

• When concatenating paths, always use \TYPO3\Flow\Utility\Files::concatenatePaths() to avoid trouble.

PHP in General

• All code should be object oriented. This means there should be no functions outside classes if not absolutely necessary. If you need a "container" for some helper methods, consider creating a static class.
• All code must make use of PHP5 advanced features for object oriented programming.
  • Use PHP namespaces
  • Always declare the scope (public, protected, private) of methods and member variables
  • Make use of iterators and exceptions, have a look at the SPL
• Make use of type-hinting wherever possible
• Always use <?php as opening tags (never only <?)
• Always use the closing tag ?> at the end of a file, don't leave it out (this ain't no Zend Framework, dude)
• Never use the shut-up operator @ to suppress error messages. It makes debugging harder, is dirty style and slow as hell
• Prefer strict comparisons whenever possible, to avoid problems with truthy and falsy values that might behave different than what you expect. Here are some examples:
  Examples of good and bad comparisons:

  if ($template)             // BAD
  if (isset($template))      // GOOD
  if ($template !== NULL))   // GOOD
  if ($template !== ''))     // GOOD
  
  if (strlen($template) > 0) // BAD! strlen("-1") is greater than 0
  if (is_string($template) && strlen($template) > 0) // BETTER
  
  if ($foo == $bar)          // BAD, avoid truthy comparisons
  if ($foo != $bar)          // BAD, avoid falsy comparisons
  if ($foo === $bar))        // GOOD
  if ($foo !== $bar))        // GOOD
  

  
  

  Truthy and falsy are fuzzy...
• Order of methods in classes. To gain a better overview, it helps if methods in classes are always ordered in a certain way. We prefer the following:
  • constructor
  • injection methods
  • initialization methods (including initializeObject())
  • public methods
  • protected methods
  • private methods
  • shutdown methods
  • destructor
• Avoid double-negation. Instead of exportSystemView(..., $noRecurse) use exportSystemView(..., $recurse). It is more logical to pass TRUE if you want recursion instead of having to pass FALSE. In general, parameters negating things are a bad idea.

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