Laminas Coding Style Guide

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

This specification extends [PSR-12][], the coding style guide and requires adherence to [PSR-1][], the basic coding standard.

Like [PSR-12][], the intent of this specification is to reduce cognitive friction when scanning code from different authors contributing to Laminas. It does so by enumerating a shared set of rules and expectations about how to format PHP code.

1.1 Previous language versions

Throughout this document, any instructions MAY be ignored if they do not exist in versions of PHP supported by your project.

1.2 Example

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

<?php
declare(strict_types=1);

namespace Mezzio;

use Psr\Http\Message\ResponseInterface;
use Psr\Http\Message\ServerRequestInterface;
use Psr\Http\Server\MiddlewareInterface;
use Psr\Http\Server\RequestHandlerInterface;
use Mezzio\Router\RouteCollector;
use Laminas\HttpHandlerRunner\RequestHandlerRunner;
use Laminas\Stratigility\MiddlewarePipeInterface;

use function Laminas\Stratigility\path;

class Application implements MiddlewareInterface, RequestHandlerInterface
{
    /** [@var](https://github.com/var) MiddlewareFactory */
    private $factory;

    /** [@var](https://github.com/var) MiddlewarePipeInterface */
    private $pipeline;

    /** [@var](https://github.com/var) RouteCollector */
    private $routes;

    /** [@var](https://github.com/var) RequestHandlerRunner */
    private $runner;

    public function __construct(
        MiddlewareFactory $factory,
        MiddlewarePipeInterface $pipeline,
        RouteCollector $routes,
        RequestHandlerRunner $runner
    ) {
        $this->factory = $factory;
        $this->pipeline = $pipeline;
        $this->routes = $routes;
        $this->runner = $runner;
    }

    /**
     * Proxies to composed pipeline to handle.
     * {[@inheritDocs](https://github.com/inheritDocs)}
     */
    public function handle(ServerRequestInterface $request) : ResponseInterface
    {
        return $this->pipeline->handle($request);
    }

    /**
     * Run the application.
     *
     * Proxies to the RequestHandlerRunner::run() method.
     */
    public function run() : void
    {
        $this->runner->run();
    }
}

2. General

2.1 Basic Coding Standard

Code MUST follow all rules outlined in [PSR-1].

The term 'StudlyCaps' in PSR-1 MUST be interpreted as PascalCase where the first letter of each word is capitalized including the very first letter.

Additional Laminas rules

For consistency a bunch of older PHP features SHOULD NOT be used:

• The [short open tag][] SHOULD NOT be used.
• Deprecated features SHOULD be avoided ([[7.0]][70.deprecated], [[7.1]][71.deprecated], [[7.2]][72.deprecated], [[7.3]][73.deprecated], [[7.4]][74.deprecated])
• The [backtick operator][] MUST NOT be used.
• The [goto][] language construct SHOULD NOT be used.
• The [global][] keyword MUST NOT be used.
• The constant [PHP_SAPI][] SHOULD be used instead of the php_sapi_name() function.
• [aliases][] SHOULD NOT be used.

There MUST NOT be a space before a semicolon. Redundant semicolons SHOULD be avoided.

Non executable code MUST be removed.

There MUST be a single space after language constructs.

Parentheses MUST be omitted where possible.

PHP function calls MUST be in lowercase.

2.2 Files

Additional Laminas rules

There MAY NOT be any content before the opening tag. Inline HTML in PHP code SHOULD be avoided. All code MUST be executable and non executable code SHOULD be removed.

The declare(strict_types=1) directive MUST be declared and be the first statement in a file.

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

All PHP files MUST end with a non-blank line, terminated with a single LF.

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.

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 lines.

Blank lines MAY be added to improve readability and to indicate related blocks of code except where explicitly forbidden.

Additional Laminas rules

There MAY be maximum one blank line to improve readability and to indicate related blocks of code except where explicitly forbidden.

There MAY NOT be any blank line after opening braces and before closing braces.

There MUST NOT be more than one statement per line.

Additional Laminas rules

There MUST NOT be a space before a semicolon. Redundant semicolons SHOULD be avoided.

2.4 Indenting and Spacing

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

Additional Laminas rules

Encapsed strings MAY be used instead of concatenating strings. When concatenating strings, there MUST be a single whitespace before and after the concatenation operator. The concatenation operator MUST NOT be the at the end of a line. If multi-line concatenation is used there MUST be an indent of 4 spaces.

// Encapsed strings
$a = 'foo';
$b = 'bar';

$c = "I like $a and $b";

// Concatenating
$a = 'Hello ';
$b = $a
   . 'World!';

2.5 Keywords and Types

All PHP reserved keywords [[1]][keywords] and types [[2]][types] MUST be in lower case.

Any new types and keywords added to future PHP versions MUST be in lower case.

Short form of type keywords MUST be used i.e. bool instead of boolean, int instead of integer etc.

2.6 Variables

Additional Laminas rules

Variable names MUST be declared in camelCase.

2.7 Arrays

Additional Laminas rules

The short array syntax MUST be used to define arrays.

All values in multiline arrays must be indented with 4 spaces.

All array values must be followed by a comma, including the last value.

There MUST NOT be whitespace around the opening bracket or before the closing bracket when referencing an array.

All double arrow symbols MUST be aligned to one space after the longest array key.

$array2 = [
    'one'    => function () {
        $foo    = [1, 2, 3];
        $barBar = [
            1,
            2,
            3,
        ];
    },
    'longer' => 2,
    3        => 'three',
];

The short list syntax [...] SHOULD be used instead of list(...).

[$a, $b, $c] = [1, 2, 3];

3. Declare Statements, Namespace, and Import Statements

The header of a PHP file may consist of a number of different blocks. If present, each of the blocks below MUST be separated by a single blank line, and MUST NOT contain a blank line. Each block MUST be in the order listed below, although blocks that are not relevant may be omitted.

• Opening <?php tag.
• File-level docblock.
• One or more declare statements.
• The namespace declaration of the file.
• One or more class-based use import statements.
• One or more function-based use import statements.
• One or more constant-based use import statements.
• The remainder of the code in the file.

When a file contains a mix of HTML and PHP, any of the above sections may still be used. If so, they MUST be present at the top of the file, even if the remainder of the code consists of a closing PHP tag and then a mixture of HTML and PHP.

When the opening <?php tag is on the first line of the file, it MUST be on its own line with no other statements unless it is a file containing markup outside of PHP opening and closing tags.

Import statements MUST never begin with a leading backslash as they must always be fully qualified.

Additional Laminas rules

There MUST be a single space after the namespace keyword and there MAY NOT be a space around a namespace separator.

Import statements MUST be alphabetically sorted.

Unused import statements SHOULD be removed.

Fancy group import statements MUST NOT be used.

Each import statement MUST be on its own line.

Import statement aliases for classes, traits, functions and constants MUST be useful, meaning that aliases SHOULD only be used if a class with the same name is imported.

Classes, traits, interfaces, constants and functions MUST be imported.

The following example illustrates a complete list of all blocks:

<?php

/**
 * This file contains an example of coding styles.
 */

declare(strict_types=1);

namespace Vendor\Package;

use Vendor\Package\ClassA as A;
use Vendor\Package\ClassB;
use Vendor\Package\ClassC as C;
use Vendor\Package\SomeNamespace\ClassD as D;
use Vendor\Package\AnotherNamespace\ClassE as E;

use function Vendor\Package\functionA;
use function Vendor\Package\functionB;
use function Another\Vendor\functionC;

use const Vendor\Package\CONSTANT_A;
use const Vendor\Package\CONSTANT_B;
use const Another\Vendor\CONSTANT_C;

/**
 * FooBar is an example class.
 */
class FooBar
{
    // ... additional PHP code ...
}

Compound namespaces with a depth of more than two MUST NOT be used. Therefore the following is the maximum compounding depth allowed:

use Vendor\Package\SomeNamespace\{
    SubnamespaceOne\ClassA,
    SubnamespaceOne\ClassB,
    SubnamespaceTwo\ClassY,
    ClassZ,
};

And the following would not be allowed:

use Vendor\Package\SomeNamespace\{
    SubnamespaceOne\AnotherNamespace\ClassA,
    SubnamespaceOne\ClassB,
    ClassZ,
};

When wishing to declare strict types in files containing markup outside PHP opening and closing tags, the declaration MUST be on the first line of the file and include an opening PHP tag, the strict types declaration and closing tag.

For example:

<?php declare(strict_types=1) ?>
<html>
<body>
    <?php
        // ... additional PHP code ...
    ?>
</body>
</html>

Declare statements MUST contain no spaces and MUST be exactly declare(strict_types=1) (with an optional semi-colon terminator).

Block declare statements are allowed and MUST be formatted as below. Note position of braces and spacing:

declare(ticks=1) {
    // some code
}

4. Classes, Properties, and Methods

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

Any closing brace MUST NOT be followed by any comment or statement on the same line.

When instantiating a new class, parentheses MUST always be present even when there are no arguments passed to the constructor.

new Foo();

Additional Laminas rules

There MUST NOT be duplicate class names.

The file name MUST match the case of the terminating class name.

PHP 4 style constructors MUST NOT be used.

Correct class name casing MUST be used.

Abstract classes MUST have a Abstract prefix.

Exception classes MUST have a Exception suffix.

Interface classes MUST have a Interface suffix.

Trait classes MUST have a Trait suffix.

For self-reference a class lower-case self:: MUST be used without spaces around the scope resolution operator.

Class name resolution via ::class MUST be used instead of __CLASS__, get_class(), get_class($this), get_called_class(), get_parent_class() and string reference.

There MAY NOT be any whitespace around the double colon operator.

Unused private methods, constants and properties MUST be removed.

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 line; the closing brace for the class MUST go on the next line after the body.

Opening braces MUST be on their own line and MUST NOT be preceded or followed by a blank line.

Closing braces MUST be on their own line and MUST NOT be preceded by a blank line.

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 and, in the case of interfaces, extends 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.

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 Using traits

The use keyword used inside the classes to implement traits MUST be declared on the next line after the opening brace.

namespace Vendor\Package;

use Vendor\Package\FirstTrait;

class ClassName
{
    use FirstTrait;
}

Each individual trait that is imported into a class MUST be included one-per-line and each inclusion MUST have its own use import statement.

Additional Laminas rules

Traits MUST be sorted alphabetically.

namespace Vendor\Package;

use Vendor\Package\FirstTrait;
use Vendor\Package\SecondTrait;
use Vendor\Package\ThirdTrait;

class ClassName
{
    use FirstTrait;
    use SecondTrait;
    use ThirdTrait;
}

When the class has nothing after the use import statement, the class closing brace MUST be on the next line after the use import statement.

namespace Vendor\Package;

use Vendor\Package\FirstTrait;

class ClassName
{
    use FirstTrait;
}

Otherwise, it MUST have a blank line after the use import statement.

namespace Vendor\Package;

use Vendor\Package\FirstTrait;

class ClassName
{
    use FirstTrait;

    private $property;
}

When using the insteadof and as operators they must be used as follows taking note of indentation, spacing, and new lines.

class Talker
{
    use A, B, C {
        B::smallTalk insteadof A;
        A::bigTalk insteadof C;
        C::mediumTalk as FooBar;
    }
}

4.3 Properties and Constants

Visibility MUST be declared on all properties.

Visibility MUST be declared on all constants if your project PHP minimum version supports constant visibilities (PHP 7.1 or later).

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

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

Property names MUST NOT be prefixed with a single underscore to indicate protected or private visibility. That is, an underscore prefix explicitly has no meaning.

There MUST be a space between type declaration and property name.

Additional Laminas rules

Default null values MUST be omitted for class properties.

A property declaration looks like the following:

class ClassName
{
    public $foo; // `= null` should be omitted
    public static int $bar = 0;
}

4.4 Methods and Functions

Visibility MUST be declared on all methods.

Method names MUST NOT be prefixed with a single underscore to indicate protected or private visibility. That is, an underscore prefix explicitly has no meaning.

Method and function names MUST NOT be declared with space after the method name. The opening brace MUST go on its own 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.

Additional Laminas rules

There MUST be a single empty line between methods in a class.

The pseudo-variable $this MUST NOT be called inside a static method or function.

Returned variables SHOULD be useful and SHOULD NOT be assigned to a value and returned on the next line.

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

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

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

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

4.5 Method and Function Arguments

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

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

class ClassName
{
    public function foo(int $arg1, &$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.

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

When you have a return type declaration present, there MUST be one space after the colon followed by the type declaration. The colon and declaration MUST be on the same line as the argument list closing parenthesis with no spaces between the two characters.

class ReturnTypeVariations
{
    public function functionName(int $arg1, $arg2): string
    {
        return 'foo';
    }

    public function anotherFunction(
        string $foo,
        string $bar,
        int $baz
    ): string {
        return 'foo';
    }
}

In nullable type declarations, there MUST NOT be a space between the question mark and the type.

Additional Laminas rules

The question mark MUST be used when the default argument value is null.

class ReturnTypeVariations
{
    public function functionName(?string $arg1, ?int &$arg2 = null): ?string
    {
        return 'foo';
    }
}

When using the reference operator & before an argument, there MUST NOT be a space after it, like in the previous example.

There MUST NOT be a space between the variadic three dot operator and the argument name:

public function process(string $algorithm, ...$parts)
{
    // processing
}

When combining both the reference operator and the variadic three dot operator, there MUST NOT be any space between the two of them:

public function process(string $algorithm, &...$parts)
{
    // processing
}

4.6 abstract, final, and static

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

Additional Laminas rules

The final keyword on methods MUST be omitted in final declared classes.

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

abstract class ClassName
{
    protected static $foo;

    abstract protected function zim();

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

4.7 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.

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. A single argument being split across multiple lines (as might be the case with an anonymous function or array) does not constitute splitting the argument list itself.

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

somefunction($foo, $bar, [
  // ...
], $baz);

$app->get('/hello/{name}', function ($name) use ($app) {
    return 'Hello ' . $app->escape($name);
});

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 body MUST be on the next line after the opening brace
• 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.

Additional Laminas rules

There MUST be one single space after break and continue structures with a numeric argument argument.

Statements MUST NOT be empty, except for catch statements.

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.

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.

Expressions in parentheses MAY be split across multiple lines, where each subsequent line is indented at least once. When doing so, the first condition MUST be on the next line. The closing parenthesis and opening brace MUST be placed together on their own line with one space between them. Boolean operators between conditions MUST always be at the beginning or at the e...