PHP Styleguide

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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.

Table of Contents

  1. Overview
  2. Files
  3. Namespace and Use Declarations
  4. Classes, Properties, Constants and Methods
  5. Control Structures
  6. Further reading

1. Overview

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 
      }
  }

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2. Files

2.1. PHP Tags

PHP code MUST use the long <?php ?> tags; it MUST NOT use the other tag variations.

All PHP files MUST end with a single blank line.

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

2.2. Character Encoding

PHP code MUST use only UTF-8.

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 
    }
}

2.4. 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.

2.5. 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.

2.6. Keywords and True/False/Null

PHP [keywords] MUST be in lower case.

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

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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 ... 

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4. Classes, Properties, Constants 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 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 
}

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 MUST be declared in $under_score annotation.

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 StarWars\People;
 
class Sith 
{
    public $dark_side = true;
}

4.3. 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';
}

4.4. 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 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 
    }
}

4.5. 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 
    }
}

4.6. 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 
    }
}

4.7. 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.

<?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
);

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5. Control Structures

The general style rules for control structures are as follows:

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.

Always use try/catch in your classes/methods so if an error arises, you have the control in what to do with that error.

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

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6. Further reading

If you want to become a PHP rockstar, you should always review:

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