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Taiwen Jiang edited this page Aug 9, 2013 · 22 revisions

Pi Engine PHP Coding Standards

By Taiwen Jiang, last update: August 7th, 2013

Check Pi Selected Standards for selected rules.

Table Of Contents

Overview

PSR-1

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

  • 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.

PSR-2

  • 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 line, and closing braces MUST go on the next line after the body.

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

  • 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.

Example

<?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
    }
}

Files

Basic

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.

PHP Tags

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

Character Encoding

PHP code MUST use only UTF-8 without BOM.

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
    }
}

Coding Style

Lines

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.

Indenting

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

Keywords and True/False/Null

PHP [keywords][] MUST be in lower case.

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

Strings

When a string is literal, the apostrophe '`' or single quote ' SHOULD be used.

Variable substitution SHOULD use the form $greeting = "Hello {$name}, welcome back!";.

When concatenating strings with the "." operator, each successive line SHOULD be padded with white space such that the "." operator is aligned under the "=" operator.

$sql = "SELECT {{id}}, {{name}} FROM {{people}} "
     . "WHERE {{name}} = 'Susan' "
     . "ORDER BY {{name}} ASC ";

Arrays

A trailing space MUST be added after each comma delimiter to improve readability.

$sampleArray = array(1, 2, 3, 'Pi', 'Engine');

Numerically indexed arrays with multi-line elements with first element on a new line.

$sampleArray = array(
    1, 2, 3, 'Zend', 'Studio',
    $a, $b, $c,
    56.44, $d, 500,
);

Numerically indexed arrays with multi-line elements with first element on the same line discouraged: each successive line MUST be padded with spaces such that the beginning of each line is aligned with the initial element.

$sampleArray = array(1, 2, 3, 'Zend', 'Studio',
                     $a, $b, $c,
                     56.44, $d, 500);

Associative arrays with multi-line elements and first element on a new line: the various => assignment operators SHOULD be padded such that they align, only one element per line.

$sampleArray = array(
    'firstKey'  => 'firstValue',
    'secondKey' => 'secondValue',
);

Associative arrays with multi-line elements and first element on same line discouraged: each successive line MUST be padded with white space such that both the keys and the values are aligned.

$sampleArray = array('firstKey'  => 'firstValue',
                     'secondKey' => 'secondValue');

Namespace and Class Names

Class names MUST be declared in StudlyCaps.

Code MUST use formal namespaces.

For example:

<?php
namespace Vendor\Model;

class Foo
{
}

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 ...

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.

<?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
}

Class Constants, Properties, and Methods

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

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';
}

Properties

Property names MUST be declared in $camelCase.

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 $fooProperty = null;
}

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
    }
}

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
    }
}

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
    }
}

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
);

Control Structures

  • 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.

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.

For multi-line conditional statements with several clauses, break the line prior to a logic operator, and pad the line such that it aligns under the first character of the conditional clause. The closing paren in the conditional will then be placed on a line with the opening brace, with one space separating the two, at an indentation level equivalent to the opening control statement.

if (($a == $b)
    && ($b == $c)
    || (Foo::CONST == $d)
) {
    $a = $d;
}

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;
}

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);

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
}

foreach

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

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

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
}

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
);

Inline Documentation

  • All documentation blocks ("docblocks") MUST be compatible with the phpDocumentor format.

  • All class files MUST contain a "file-level" docblock at the top of each file and a "class-level" docblock immediately above each class.

  • "file-level" docblock contains phpDocumentor tags at a minimum:

/**
 * Pi Engine (http://pialog.org/)
 *
 * @link      http://code.pialog.org for the Pi Engine source repository
 * @copyright Copyright (c) Pi Engine (http://pialog.org/)
 * @license   http://www.pialog.org/license.txt New BSD License
 */
  • "class-level" docblock contains phpDocumentor tags at a minimum:
/**
 * Short description for class
 *
 * Long description for class (if any)...
 *
 * Sample code:
 *
 * <code>
 *   $someCodeForUseExample;
 * </code>
 *
 * @author    Author Name <[author_email_address]>
 */
  • Every function/method MUST have a docblock that contains at a minimum:
    • A description of the function
    • All of the arguments
    • All of the possible return values (even void)
    /**
     * Load a service
     *
     * @param string    $name
     * @param array     $options
     * @return Service\AbstractService
     * @throws \Exception
     */
    public function load($name, $options = array())
    {
  • Use @throws for all known exception classes:
@throws exceptionclass [description]
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