Kent Standards

Usage

This style guide is derived from PSR-2 but has been modified slightly for the University of Kent development teams. This product is publicly available under the terms of the MIT license included in this repository. Please refer to the current brand guidelines for use of the existing brand.

University of Kent Coding Standards and Style Guide

This document 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 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.

PHP Code Sniffer

A PHP Code Sniffer ruleset along with custom sniffs is in the phpcs\kentStandard folder. This ruleset implements most, but not all, of the rules outlined below. To use this you must install PHP Code Sniffer and make phpcs and phpcbf avaliable on your path.

This ruleset can be used on the command line and by editors such as VS Code to automatically flag or fix errors.

In the commands below assume that the kentStandards repo is checked out at ~/Code/kentStandards

Examples:

1. To list errors in a specific file

phpcs --standard=~/Code/KentStandards/phpcs/kentStandard/ruleset.xml file.php

2. To fix errors in a specific file when possible

phpcbf --standard=~/Code/KentStandards/phpcs/kentStandard/ruleset.xml file.php

1. General

1.1. PHP Tags

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

1.2. Character Encoding

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

1.3. Line Endings

• All PHP files SHOULD use use the Unix LF (linefeed) line ending. Whatever line ending is used it MUST be used consitently throughout a project.

1.4. Whitespace & Indentation

• All PHP files MUST end with a single blank line.

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

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

• Single blank lines MAY be added to improve readability and to indicate related blocks of code.

• Code MUST use tabs for indentation, and MUST NOT use spaces for indenting.

• The use of spaces is permitted for fine-grained inter-line alignment of operators, values etc.

1.5. Lines

• There MUST NOT be more than one statement per line.

• 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.

1.6. Keywords and True/False/Null

• PHP keywords MUST be in lower case.

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

1.7. 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
    }
}

2. Namespace, Use Declarations and Class Names

• Namespaces and classes MUST follow PSR-4 "autoloading". 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.

• 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 ...

• 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
{
}

• 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.

<?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
}

3. Class Constants, Properties, and Methods

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

3.1. 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';
}

3.2. Properties

• Properties and Variables MUST use an underscore format. For example $variable_name.

• 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;
}

3.3. Methods

• Method names MUST be declared in camelCase().

• 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 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.

• 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
    }
}

• 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
    }
}

3.4. 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 ClassName
{
    protected static $foo;

    abstract protected function zim();

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

4. 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.

• Colon notation MUST NOT be used. I.E :

if(true) :  
  //stuff here
endif;

5.1. if, elseif, else if, else

• An if structure looks like the following. Note the placement of parentheses, spaces, and braces; and that else and elseif or else if 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
}

• Avoid the use of $k, $v, $key, $value etc. for variables within a foreach, names SHOULD be descriptive.

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
}

5.7. Ternary statements

• Ternary statments MUST NOT be nested. Use other approriate control structues nested with correct indentation.

• There MUST be one space both before and after the ? and : in a ternary expresion. ?: is permited when ther is no `true' case.

• There MUST be braces surrounding the condition if it contains any form of expression, i.e. is not simply a variable or boolean.

## 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
);