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PHP Coding Standards

Shameless Copy of Symfony Coding Standards

These standards are borrowed from the Symfony Standards. They are edited by Digitec when appropriate. All of the examples below have been edited to reflect Digitec changes.

KD7 will follow the standards defined in the PSR-0, PSR-1 and PSR-2 documents.

Remember that the main advantage of standards is that every piece of code looks and feels familiar, it's not about this or that being more readable.

Since a picture - or some code - is worth a thousand words, here's a short example containing most features described below:

<?php

/**
 * (c) Digitec Interactive 2014. All rights reserved.
 *
 * Author: rwilbert
 *
 * Date: mm/dd/yyyy
 */

namespace Acme;

/**
 * Coding standards demonstration.
 */
class FooBar implements MySimpleInterface {

    use MySimpleTrait;

    const SOME_CONST = 42;

    private $fooBar;

    /**
     * @param string $dummy Some argument description
     */
    public function __construct($dummy) {
        $this->fooBar = $this->transformText($dummy);
    }

    /**
     * @param string $dummy Some argument description
     * @param array  $options
     *
     * @return string|null Transformed input
     *
     * @throws \RuntimeException
     */
    private function transformText($dummy, array $options = array()) {
        $mergedOptions = array_merge(
            array(
                'some_default' => 'values',
                'another_default' => 'more values',
            ),
            $options
        );

        if (true === $dummy) {
            return;
        }
        if ('string' === $dummy) {
            if ('values' === $mergedOptions['some_default']) {
                return substr($dummy, 0, 5);
            }

            return ucwords($dummy);
        }
        throw new \RuntimeException(sprintf('Unrecognized dummy option "%s"', $dummy));
    }
}

Structure

• Add a single space after each comma delimiter;
• Add a single space around operators (==, &&, ...);
• Add a comma after each array item in a multi-line array, even after the last one;
• Add a blank line before return statements, unless the return is alone inside a statement-group (like an if statement);
• Use braces to indicate control structure body regardless of the number of statements it contains;
• Define one class per file - this does not apply to private helper classes that are not intended to be instantiated from the outside and thus are not concerned by the PSR-0 standard;
• Declare class properties before methods;
• Declare public methods first, then protected ones and finally private ones;
• Use parentheses when instantiating classes regardless of the number of arguments the constructor has;
• Exception message strings should be concatenated using sprintf.

Naming Conventions

• Use camelCase, not underscores, for variable, function and method names, arguments;
• Use underscores for array keys, option names and parameter names;
• Use namespaces for all classes;
• Prefix abstract classes with Abstract;
• Suffix interfaces with Interface;
• Suffix traits with Trait;
• Suffix exceptions with Exception;
• Use alphanumeric characters and underscores for file names;

Service Naming Conventions

• A service name contains groups, separated by dots;
• The DI alias of the bundle is the first group (e.g. fos_user);
• Use lowercase letters for service and parameter names;
• A group name uses the underscore notation;
• Each service has a corresponding parameter containing the class name, following the SERVICE NAME.class convention.

Method Names (Optional)

When an object has a "main" many relation with related "things" (objects, parameters, ...), the method names are normalized:

get() set() has() all() replace() remove() clear() isEmpty() add() register() count() keys()

The usage of these methods are only allowed when it is clear that there is a main relation:

• a CookieJar has many Cookie objects;
• a Service Container has many services and many parameters (as services is the main relation, the naming convention is used for this relation);
• a Console Input has many arguments and many options. There is no "main" relation, and so the naming convention does not apply.

For many relations where the convention does not apply, the following methods must be used instead (where XXX is the name of the related thing):

While "setXXX" and "replaceXXX" are very similar, there is one notable difference: "setXXX" may replace, or add new elements to the relation. "replaceXXX", on the other hand, cannot add new elements. If an unrecognized key as passed to "replaceXXX" it must throw an exception.

Documentation

• Add PHPDoc blocks for all classes, methods, and functions;

• Omit the @return tag if the method does not return anything;

• The @package and @subpackage annotations are not used.

PSR-0

Autoloading Standard

The following describes the mandatory requirements that must be adhered to for autoloader interoperability.

Mandatory

• A fully-qualified namespace and class must have the following structure \<Vendor Name>\(<Namespace>\)*<Class Name>
• Each namespace must have a top-level namespace ("Vendor Name").
• Each namespace can have as many sub-namespaces as it wishes.
• Each namespace separator is converted to a DIRECTORY_SEPARATOR when loading from the file system.
• Each _ character in the CLASS NAME is converted to a DIRECTORY_SEPARATOR. The _ character has no special meaning in the namespace.
• The fully-qualified namespace and class is suffixed with .php when loading from the file system.
• Alphabetic characters in vendor names, namespaces, and class names may be of any combination of lower case and upper case.

Examples

• \Doctrine\Common\IsolatedClassLoader => /path/to/project/lib/vendor/Doctrine/Common/IsolatedClassLoader.php
• \Symfony\Core\Request => /path/to/project/lib/vendor/Symfony/Core/Request.php
• \Zend\Acl => /path/to/project/lib/vendor/Zend/Acl.php
• \Zend\Mail\Message => /path/to/project/lib/vendor/Zend/Mail/Message.php

Underscores in Namespaces and Class Names

• \namespace\package\Class_Name => /path/to/project/lib/vendor/namespace/package/Class/Name.php
• \namespace\package_name\Class_Name => /path/to/project/lib/vendor/namespace/package_name/Class/Name.php

The standards we set here should be the lowest common denominator for painless autoloader interoperability. You can test that you are following these standards by utilizing this sample SplClassLoader implementation which is able to load PHP 5.3 classes.

Example Implementation

Below is an example function to simply demonstrate how the above proposed standards are autoloaded.

<?php

function autoload($className) {
    $className = ltrim($className, '\\');
    $fileName  = '';
    $namespace = '';
    if ($lastNsPos = strrpos($className, '\\')) {
        $namespace = substr($className, 0, $lastNsPos);
        $className = substr($className, $lastNsPos + 1);
        $fileName  = str_replace('\\', DIRECTORY_SEPARATOR, $namespace) . DIRECTORY_SEPARATOR;
    }
    $fileName .= str_replace('_', DIRECTORY_SEPARATOR, $className) . '.php';

    require $fileName;
}

SplClassLoader Implementation

The following gist is a sample SplClassLoader implementation that can load your classes if you follow the autoloader interoperability standards proposed above. It is the current recommended way to load PHP 5.3 classes that follow these standards.

• http://gist.github.com/221634

PSR-1

Basic Coding Standard

This section of the standard comprises what should be considered the standard coding elements that are required to ensure a high level of technical interoperability between shared PHP code.

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119.

1. Overview

• Files MUST use only <?php and <?= tags.

Digitec code MUST use only the <?php tags.

• Files MUST use only UTF-8 without BOM for PHP code.

• Files SHOULD either declare symbols (classes, functions, constants, etc.) or cause side-effects (e.g. generate output, change .ini settings, etc.) but SHOULD NOT do both.

• Namespaces and classes MUST follow an "autoloading" PSR: [PSR-0, PSR-4].

• Class names MUST be declared in StudlyCaps.

• Class constants MUST be declared in all upper case with underscore separators.

• Method names MUST be declared in camelCase.

2. Files

2.1. PHP Tags

PHP code MUST use the long <?php ?> tags or the short-echo <?= ?> tags ; it MUST NOT use the other tag variations.

Digitec code MUST use only the <?php ?> tags.

2.2. Character Encoding

PHP code MUST use only UTF-8 without BOM.

2.3. Side Effects

A file SHOULD declare new symbols (classes, functions, constants, etc.) and cause no other side effects, or it SHOULD execute logic with side effects, but SHOULD NOT do both.

The phrase "side effects" means execution of logic not directly related to declaring classes, functions, constants, etc., merely from including the file.

"Side effects" include but are not limited to: generating output, explicit use of require or include, connecting to external services, modifying ini settings, emitting errors or exceptions, modifying global or static variables, reading from or writing to a file, and so on.

The following is an example of a file with both declarations and side effects; i.e, an example of what to avoid:

<?php
// side effect: change ini settings
ini_set('error_reporting', E_ALL);

// side effect: loads a file
include "file.php";

// side effect: generates output
echo "<html>\n";

// declaration
function foo() {
    // function body
}

The following example is of a file that contains declarations without side effects; i.e., an example of what to emulate:

<?php
// declaration
function foo() {
    // function body
}

// conditional declaration is *not* a side effect
if (! function_exists('bar')) {
    function bar()
    {
        // function body
    }
}

3. Namespace and Class Names

Namespaces and classes MUST follow PSR-0.

This means each class is in a file by itself, and is in a namespace of at least one level: a top-level vendor name.

Class names MUST be declared in StudlyCaps.

Code written for PHP 5.3 and after MUST use formal namespaces.

For example:

<?php
// PHP 5.3 and later:
namespace Vendor\Model;

class Foo {
}

Code written for 5.2.x and before SHOULD use the pseudo-namespacing convention of Vendor_ prefixes on class names.

<?php
// PHP 5.2.x and earlier:
class Vendor_Model_Foo {
}

4. Class Constants, Properties, and Methods

The term "class" refers to all classes, interfaces, and traits.

4.1. Constants

Class constants MUST be declared in all upper case with underscore separators. For example:

<?php
namespace Vendor\Model;

class Foo {
    const VERSION = '1.0';
    const DATE_APPROVED = '2012-06-01';
}

4.2. Properties

This guide intentionally avoids any recommendation regarding the use of $StudlyCaps, $camelCase, or $under_score property names.

Whatever naming convention is used SHOULD be applied consistently within a reasonable scope. That scope may be vendor-level, package-level, class-level, or method-level.

Digitec code MUST follow the Symfony Naming Conventions.

4.3. Methods

Method names MUST be declared in camelCase().

PSR-2

Coding Style Guide

This guide extends and expands on PSR-1, the basic coding standard.

The intent of this guide is to reduce cognitive friction when scanning code from different authors. It does so by enumerating a shared set of rules and expectations about how to format PHP code.

The style rules herein are derived from commonalities among the various member projects. When various authors collaborate across multiple projects, it helps to have one set of guidelines to be used among all those projects. Thus, the benefit of this guide is not in the rules themselves, but in the sharing of those rules.

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119.

1. Overview

• Code MUST follow a "coding style guide" PSR [PSR-1].

• Code MUST use 4 spaces for indenting, not tabs.

• There MUST NOT be a hard limit on line length; the soft limit MUST be 120 characters; lines SHOULD be 80 characters or less.

• There MUST be one blank line after the namespace declaration, and there MUST be one blank line after the block of use declarations.

• Opening braces for classes MUST go on the next same line, and closing braces MUST go on the next line after the body.

In Digitec code, the opening brace for classes MUST go on the same line.

• Opening braces for methods MUST go on the next same line, and closing braces MUST go on the next line after the body.

In Digitec code, the opening brace for methods MUST go on the same line.

• Visibility MUST be declared on all properties and methods; abstract and final MUST be declared before the visibility; static MUST be declared after the visibility.

• Control structure keywords MUST have one space after them; method and function calls MUST NOT.

• Opening braces for control structures MUST go on the same line, and closing braces MUST go on the next line after the body.

• Opening parentheses for control structures MUST NOT have a space after them, and closing parentheses for control structures MUST NOT have a space before.

1.1. Example

This example encompasses some of the rules below as a quick overview:

<?php
namespace Vendor\Package;

use FooInterface;
use BarClass as Bar;
use OtherVendor\OtherPackage\BazClass;

class Foo extends Bar implements FooInterface {
    public function sampleFunction($a, $b = null) {
        if ($a === $b) {
            bar();
        } elseif ($a > $b) {
            $foo->bar($arg1);
        } else {
            BazClass::bar($arg2, $arg3);
        }
    }

    final public static function bar() {
        // method body
    }
}

2. General

2.1 Basic Coding Standard

Code MUST follow all rules outlined in PSR-1.

2.2 Files

All PHP files MUST use the Unix LF (linefeed) line ending.

All PHP files MUST end with a single blank line.

The closing ?> tag MUST be omitted from files containing only PHP.

2.3. Lines

There MUST NOT be a hard limit on line length.

The soft limit on line length MUST be 120 characters; automated style checkers MUST warn but MUST NOT error at the soft limit.

Lines SHOULD NOT be longer than 80 characters; lines longer than that SHOULD be split into multiple subsequent lines of no more than 80 characters each.

There MUST NOT be trailing whitespace at the end of non-blank lines.

Blank lines MAY be added to improve readability and to indicate related blocks of code.

There MUST NOT be more than one statement per line.

2.4. Indenting

Code MUST use an indent of 4 spaces, and MUST NOT use tabs for indenting.

N.b.: Using only spaces, and not mixing spaces with tabs, helps to avoid problems with diffs, patches, history, and annotations. The use of spaces also makes it easy to insert fine-grained sub-indentation for inter-line alignment.

2.5. Keywords and True/False/Null

PHP keywords MUST be in lower case.

The PHP constants true, false, and null MUST be in lower case.

3. Namespace and Use Declarations

When present, there MUST be one blank line after the namespace declaration.

When present, all use declarations MUST go after the namespace declaration.

There MUST be one use keyword per declaration.

There MUST be one blank line after the use block.

For example:

<?php
namespace Vendor\Package;

use FooClass;
use BarClass as Bar;
use OtherVendor\OtherPackage\BazClass;

// ... additional PHP code ...

4. Classes, Properties, and Methods

The term "class" refers to all classes, interfaces, and traits.

4.1. Extends and Implements

The extends and implements keywords MUST be declared on the same line as the class name.

The opening brace for the class MUST go on its own the same line; the closing brace for the class MUST go on the next line after the body.

In Digitec code, the opening brace for classes MUST go on the same line.

<?php
namespace Vendor\Package;

use FooClass;
use BarClass as Bar;
use OtherVendor\OtherPackage\BazClass;

class ClassName extends ParentClass implements \ArrayAccess, \Countable {
    // constants, properties, methods
}

Lists of implements MAY be split across multiple lines, where each subsequent line is indented once. When doing so, the first item in the list MUST be on the next line, and there MUST be only one interface per line.

<?php
namespace Vendor\Package;

use FooClass;
use BarClass as Bar;
use OtherVendor\OtherPackage\BazClass;

class ClassName extends ParentClass implements
    \ArrayAccess,
    \Countable,
    \Serializable {
    // constants, properties, methods
}

4.2. Properties

Visibility MUST be declared on all properties.

The var keyword MUST NOT be used to declare a property.

There MUST NOT be more than one property declared per statement.

Property names SHOULD NOT be prefixed with a single underscore to indicate protected or private visibility.

A property declaration looks like the following.

<?php
namespace Vendor\Package;

class ClassName {
    public $foo = null;
}

4.3. Methods

Visibility MUST be declared on all methods.

Method names SHOULD NOT be prefixed with a single underscore to indicate protected or private visibility.

Method names MUST NOT be declared with a space after the method name. The opening brace MUST go on its own the same line, and the closing brace MUST go on the next line following the body. There MUST NOT be a space after the opening parenthesis, and there MUST NOT be a space before the closing parenthesis.

In Digitec code, the opening brace for methods MUST go on the same line.

A method declaration looks like the following. Note the placement of parentheses, commas, spaces, and braces:

<?php
namespace Vendor\Package;

class ClassName {
    public function fooBarBaz($arg1, &$arg2, $arg3 = []) {
        // method body
    }
}

4.4. Method Arguments

In the argument list, there MUST NOT be a space before each comma, and there MUST be one space after each comma.

Method arguments with default values MUST go at the end of the argument list.

<?php
namespace Vendor\Package;

class ClassName {
    public function foo($arg1, &$arg2, $arg3 = []) {
        // method body
    }
}

Argument lists MAY be split across multiple lines, where each subsequent line is indented once. When doing so, the first item in the list MUST be on the next line, and there MUST be only one argument per line.

When the argument list is split across multiple lines, the closing parenthesis and opening brace MUST be placed together on their own line with one space between them.

<?php
namespace Vendor\Package;

class ClassName {
    public function aVeryLongMethodName(
        ClassTypeHint $arg1,
        &$arg2,
        array $arg3 = [] 
    ) {
        // method body
    }
}

4.5. abstract, final, and static

When present, the abstract and final declarations MUST precede the visibility declaration.

When present, the static declaration MUST come after the visibility declaration.

<?php
namespace Vendor\Package;

abstract class AbstractClassName {
    protected static $foo;

    abstract protected function zim();

    final public static function bar() {
        // method body
    }
}

4.6. Method and Function Calls

When making a method or function call, there MUST NOT be a space between the method or function name and the opening parenthesis, there MUST NOT be a space after the opening parenthesis, and there MUST NOT be a space before the closing parenthesis. In the argument list, there MUST NOT be a space before each comma, and there MUST be one space after each comma.

<?php
bar();
$foo->bar($arg1);
Foo::bar($arg2, $arg3);

Argument lists MAY be split across multiple lines, where each subsequent line is indented once. When doing so, the first item in the list MUST be on the next line, and there MUST be only one argument per line.

<?php
$foo->bar(
    $longArgument,
    $longerArgument,
    $muchLongerArgument
);

5. Control Structures

The general style rules for control structures are as follows:

• There MUST be one space after the control structure keyword
• There MUST NOT be a space after the opening parenthesis
• There MUST NOT be a space before the closing parenthesis
• There MUST be one space between the closing parenthesis and the opening brace
• The structure body MUST be indented once
• The closing brace MUST be on the next line after the body

The body of each structure MUST be enclosed by braces. This standardizes how the structures look, and reduces the likelihood of introducing errors as new lines get added to the body.

5.1. if, elseif, else

An if structure looks like the following. Note the placement of parentheses, spaces, and braces; and that else and elseif are on the same line as the closing brace from the earlier body.

<?php
if ($expr1) {
    // if body
} elseif ($expr2) {
    // elseif body
} else {
    // else body;
}

The keyword elseif SHOULD be used instead of else if so that all control keywords look like single words.

5.2. switch, case

A switch structure looks like the following. Note the placement of parentheses, spaces, and braces. The case statement MUST be indented once from switch, and the break keyword (or other terminating keyword) MUST be indented at the same level as the case body. There MUST be a comment such as // no break when fall-through is intentional in a non-empty case body.

<?php
switch ($expr) {
    case 0:
        echo 'First case, with a break';
        break;
    case 1:
        echo 'Second case, which falls through';
        // no break
    case 2:
    case 3:
    case 4:
        echo 'Third case, return instead of break';
        return;
    default:
        echo 'Default case';
        break;
}

5.3. while, do while

A while statement looks like the following. Note the placement of parentheses, spaces, and braces.

<?php
while ($expr) {
    // structure body
}

Similarly, a do while statement looks like the following. Note the placement of parentheses, spaces, and braces.

<?php
do {
    // structure body;
} while ($expr);

5.4. for

A for statement looks like the following. Note the placement of parentheses, spaces, and braces.

<?php
for ($i = 0; $i < 10; $i++) {
    // for body
}

5.5. foreach

A foreach statement looks like the following. Note the placement of parentheses, spaces, and braces.

<?php
foreach ($iterable as $key => $value) {
    // foreach body
}

5.6. try, catch

A try catch block looks like the following. Note the placement of parentheses, spaces, and braces.

<?php
try {
    // try body
} catch (FirstExceptionType $e) {
    // catch body
} catch (OtherExceptionType $e) {
    // catch body
}

6. Closures

Closures MUST be declared with a space after the function keyword, and a space before and after the use keyword.

The opening brace MUST go on the same line, and the closing brace MUST go on the next line following the body.

There MUST NOT be a space after the opening parenthesis of the argument list or variable list, and there MUST NOT be a space before the closing parenthesis of the argument list or variable list.

In the argument list and variable list, there MUST NOT be a space before each comma, and there MUST be one space after each comma.

Closure arguments with default values MUST go at the end of the argument list.

A closure declaration looks like the following. Note the placement of parentheses, commas, spaces, and braces:

<?php
$closureWithArgs = function ($arg1, $arg2) {
    // body
};

$closureWithArgsAndVars = function ($arg1, $arg2) use ($var1, $var2) {
    // body
};

Argument lists and variable lists MAY be split across multiple lines, where each subsequent line is indented once. When doing so, the first item in the list MUST be on the next line, and there MUST be only one argument or variable per line.

When the ending list (whether or arguments or variables) is split across multiple lines, the closing parenthesis and opening brace MUST be placed together on their own line with one space between them.

The following are examples of closures with and without argument lists and variable lists split across multiple lines.

<?php
$longArgs_noVars = function (
    $longArgument,
    $longerArgument,
    $muchLongerArgument
) {
   // body
};

$noArgs_longVars = function () use (
    $longVar1,
    $longerVar2,
    $muchLongerVar3
) {
   // body
};

$longArgs_longVars = function (
    $longArgument,
    $longerArgument,
    $muchLongerArgument
) use (
    $longVar1,
    $longerVar2,
    $muchLongerVar3
) {
   // body
};

$longArgs_shortVars = function (
    $longArgument,
    $longerArgument,
    $muchLongerArgument
) use ($var1) {
   // body
};

$shortArgs_longVars = function ($arg) use (
    $longVar1,
    $longerVar2,
    $muchLongerVar3
) {
   // body
};

Note that the formatting rules also apply when the closure is used directly in a function or method call as an argument.

<?php
$foo->bar(
    $arg1,
    function ($arg2) use ($var1) {
        // body
    },
    $arg3
);

7. Conclusion

There are many elements of style and practice intentionally omitted by this guide. These include but are not limited to:

• Declaration of global variables and global constants

• Declaration of functions

• Operators and assignment

• Inter-line alignment

• Comments and documentation blocks

• Class name prefixes and suffixes

• Best practices

Future recommendations MAY revise and extend this guide to address those or other elements of style and practice.

References

• PSR-0
• PSR-1
• PSR-2
• Symfony Coding Standards