Taken from the Zend Framework PHP coding standards, The document was altered and modified to use with Yii framework. If you see anything that needs improvement let me know and i will update it.

Yii – PHP Coding Standards (draft)


This document provides the coding standards and guidelines for developers and teams working together on projects. The subjects covered are:

  • PHP File Formatting
  • Naming Conventions
  • Coding Style
  • Inline Documentation
  • Errors and Exceptions


Good coding standards are important in any development project, particularly when multiple developers are working on the same project. Having coding standards helps to ensure that the code is of high quality, has fewer bugs, and is easily maintained.

Abstract goals we strive for:

  • extreme simplicity
  • Tool friendliness, such as use of method signatures, constants, and patterns that support IDE tools and auto-completion of method, class, and constant names.

When considering the goals above, each situation requires an examination of the circumstances and balancing of various trade-offs.

PHP File Formatting


For files that contain only PHP code, the closing tag (“?>”) is to be omitted. It is not required by PHP, and omitting it prevents trailing whitespace from being accidentally injected into the output.


Inclusion of arbitrary binary data as permitted by __HALT_COMPILER () is prohibited from any PHP file or files derived from them. Use of this feature is only permitted for special installation scripts.


Use an indent of 4 spaces with no tab characters. Editors should be configured to treat tabs as spaces in order to prevent injection of tab characters into the source code.

Maximum Line Length

The target line length is 80 characters; i.e., developers should aim keep code as close to the 80-column boundary as is practical. However, longer lines are acceptable. The maximum length of any line of PHP code is 120 characters.

Line Termination

Line termination is the standard way for UNIX text files. Lines must end only with a linefeed (LF). Linefeeds are represented as ordinal 10, or hexadecimal 0x0A.

Do not use carriage returns (CR) like Macintosh computers (0x0D).

Do not use the carriage return/linefeed combination (CRLF) as Windows computers (0x0D, 0x0A).

Lines should not contain trailing spaces. In order to facilitate this convention, most editors can be configured to strip trailing spaces, such as upon a save operation.

Naming Conventions

Abstractions Used in API (Class Interfaces)

When creating an API for use by application developers if application developers must identify abstractions using a compound name, separate the names using underscores, not camelCase. For example, the name used for the MySQL PDO driver is ‘pdo_mysql’, not ‘pdoMysql’. When the developer uses a string, normalize it to lowercase. Where reasonable, add constants to support this (e.g. PDO_MYSQL).


The Yii Framework employs a class naming convention whereby the names of the classes directly map to the directories in which they are stored. The root level directory of the Yii Framework is the “framework/” directory, under which all classes are stored hierarchically.

Class names may only contain alphanumeric characters. Numbers are permitted in class names but are discouraged. Dot (.) is only permitted in place of the path separator. For example, the filename "framework/web/CController.php" must map to the class name "CController".
Yii uses path aliases extensively. A path alias is associated with a directory or file path. It is specified in dot syntax, similar to that of widely adopted namespace format:
* system: refers to the Yii framework directory; 
* application: refers to the application's base directory; 
* webroot: refers to the directory containing the entry script file. This alias has been available since version 1.0.3
It will be mapped under the Yii framework as ‘system.web.ccontroller’ using the Yii:import method. 

If a class name is comprised of more than one word, the first letter of each new word must be capitalized. Successive capitalized letters are not allowed; e.g., a class “Test_CLASS” is not allowed, while “Test_Class” is acceptable.

Yii Framework classes that are authored by Yii or one of the participating partner companies and distributed with the Framework must always start with the letter “C” and must be stored under the “framework/” directory hierarchy accordingly.

These are examples of acceptable names for classes:





Code that operates with the framework but is not part of the framework, such as code written by a framework end-user and not Yii or one of the framework’s partner companies, must never start with “C”


Interface classes must follow the same conventions as other classes (see above), but must end with “_Interface”, such as in these examples:



For all other files, only alphanumeric characters, underscores, and the dash character (“-“) are permitted. Spaces are prohibited.

Any file that contains any PHP code must end with the extension “.php” (except View scripts, which end in “.phtml” by default). These examples show the acceptable filenames for containing the class names from the examples in the section above:




File names must follow the mapping to class names described above.

Functions and Methods

Function names may only contain alphanumeric characters. Underscores are not permitted. Numbers are permitted in function names but are discouraged.

Function names must always start with a lowercase letter. When a function name consists of more than one word, the first letter of each new word must be capitalized. This is commonly called the “camelCase” method.

Verbosity is encouraged. Function names should be as illustrative as is practical to enhance understanding.

These are examples of acceptable names for functions:




For object-oriented programming, accessors for object members should always be prefixed with either “get” or “set”. When using design patterns, such as the Singleton or Factory patterns, the name of the method should contain the pattern name where practical to make the pattern more readily recognizable.

Though function names may not contain the underscore character, class methods that are declared as protected or private must begin with a single underscore, as in the following example:

class Foo_Bar


protected function _fooBar()


// …



Functions in the global scope, or “floating functions,” are permitted but discouraged. It is recommended that these functions be wrapped in a class and declared static.

Functions or variables declared with a “static” scope in a class generally should not be “private”, but protected instead. Use “final” if the function should not be extended.

Optional Parameters

Use “null” as the default value instead of “false”, for situations like this:

public function foo($required, $optional = null)

When $optional does not have or need a particular default value.

However, if an optional parameter is boolean, and its logical default value should be true, or false, then using true or false is acceptable.


Variable names may only contain alphanumeric characters. Underscores are not permitted. Numbers are permitted in variable names but are discouraged.

For class member variables that are declared with the private or protected construct, the first character of the variable name must be a single underscore. This is the only acceptable usage of an underscore in a variable name. Member variables declared as “public” may never start with an underscore. For example:

class Foo_Bar


protected $_bar;


Like function names, variable names must always start with a lowercase letter and follow the “camelCase” capitalization convention.

Verbosity is encouraged. Variable names should always be as verbose as practical. Terse variable names such as “$i” and “$n” are discouraged for anything other than the smallest loop contexts. If a loop contains more than 20 lines of code, variables for such indices or counters need to have more descriptive names.


Constants may contain both alphanumeric characters and the underscore. Numbers are permitted in constant names.

Constant names must always have all letters capitalized.

To enhance readability, words in constant names must be separated by underscore characters. For example, “EMBED_SUPPRESS_EMBED_EXCEPTION” is permitted but “EMBED_SUPPRESSEMBEDEXCEPTION” is not.

Constants must be defined as class members by using the “const” construct. Defining constants in the global scope with “define” is permitted but discouraged.

Booleans and the NULL Value

Unlike PHP’s documentation, the Yii Framework uses lowercase for both boolean values and the “null” value.

Coding Style

PHP Code Demarcation

PHP code must always be delimited by the full-form, standard PHP tags (although you should see the note about the closing PHP tag):



Short tags are never allowed.


String Literals

When a string is literal (contains no variable substitutions), the apostrophe or “single quote” must always used to demarcate the string:

$a = ‘Example String’;

String Literals Containing Apostrophes

When a literal string itself contains apostrophes, it is permitted to demarcate the string with quotation marks or “double quotes”. This is especially encouraged for SQL statements:

$sql = “SELECT `id`, `name` from `people` WHERE `name`=’Fred’ OR `name`=’Susan'”;

The above syntax is preferred over escaping apostrophes.

Variable Substitution

Variable substitution is permitted using either of these two forms:

$greeting = “Hello $name, welcome back!”;

$greeting = “Hello {$name}, welcome back!”;

For consistency, this form is not permitted:

$greeting = “Hello ${name}, welcome back!”;

String Concatenation

Strings may be concatenated using the “.” operator. A space must always be added before and after the “.” operator to improve readability:

$company = ‘This’ . ‘ is’ . ‘ a test’;

When concatenating strings with the “.” operator, it is permitted to break the statement into multiple lines to improve readability. In these cases, each successive line should be padded with whitespace such that the “.” operator is aligned under the “=” operator:

$sql = “SELECT `id`, `name` FROM `people` ”

. “WHERE `name` = ‘Susan’ ”

. “ORDER BY `name` ASC “;


Numerically Indexed Arrays

Negative numbers are not permitted as array indices.

An indexed array may be started with any non-negative number, however this is discouraged and it is recommended that all arrays have a base index of 0.

When declaring indexed arrays with the array construct, a trailing space must be added after each comma delimiter to improve readability:

$sampleArray = array(1, 2, 3, ‘test’, ‘Yii’);

It is also permitted to declare multi-line indexed arrays using the array construct. In this case, each successive line must be padded with spaces such that beginning of each line aligns as shown below:

$sampleArray = array(1, 2, 3, ‘Zend’, ‘Studio’,

$a, $b, $c,

56.44, $d, 500);

Associative Arrays

When declaring associative arrays with the array construct, it is encouraged to break the statement into multiple lines. In this case, each successive line must be padded with whitespace such that both the keys and the values are aligned:

$sampleArray = array(‘firstKey’ => ‘firstValue’,

‘secondKey’ => ‘secondValue’);


Class Declarations

Classes must be named by following the naming conventions.

The brace is always written on the line underneath the class name (“one true brace” form).

Every class must have a documentation block that conforms to the phpDocumentor standard.

Any code within a class must be indented the standard indent of four spaces.

Only one class is permitted per PHP file.

Placing additional code in a class file is permitted but discouraged. In these files, two blank lines must separate the class from any additional PHP code in the file.

This is an example of an acceptable class declaration:


* Class Docblock Here


class Test_Class


// entire content of class

// must be indented four spaces


Class Member Variables

Member variables must be named by following the variable naming conventions.

Any variables declared in a class must be listed at the top of the class, prior to declaring any functions.

The var construct is not permitted. Member variables always declare their visibility by using one of the private, protected, or public constructs. Accessing member variables directly by making them public is permitted but discouraged in favor of accessor methods having the set and get prefixes.

Functions and Methods

Function and Method Declaration

Functions and class methods must be named by following the naming conventions.

Methods must always declare their visibility by using one of the private, protected, or public constructs.

Following the more common usage in the PHP developer community, static methods should declare their visibility first:

public static foo() { … }

private static bar() { … }

protected static goo() { … }

As for classes, the opening brace for a function or method is always written on the line underneath the function or method name (“one true brace” form). There is no space between the function or method name and the opening parenthesis for the arguments.

This is an example of acceptable class method declarations:


* Class Docblock Here


class Bar_Foo



* Method Docblock Here


public function sampleMethod($a)


// entire content of function

// must be indented four spaces



* Method Docblock Here


protected function _anotherMethod()


// …



Please note

Passing function or method arguments by reference is only permitted by defining the reference in the function or method declaration, as in the following example:

function sampleMethod(&$a)


Call-time pass by-reference is prohibited.

The return value must not be enclosed in parentheses. This can hinder readability and can also break code if a function or method is later changed to return by reference.

function foo()





return $this->bar;


The use of type hinting is encouraged where possible with respect to the component design. For example,

class Test_Component


public function foo(SomeInterface $object)


public function bar(array $options)



Where possible, try to keep your use of exceptions vs. type hinting consistent, and not mix both approaches at the same time in the same method for validating argument types. However, before PHP 5.2, “Failing to satisfy the type hint results in a fatal error,” and might fail to satisfy other coding standards involving the use of throwing exceptions. Beginning with PHP 5.2, failing to satisfy the type hint results in an E_RECOVERABLE_ERROR, requiring developers to deal with these from within a custom error handler, instead of using a try..catch block.

Function and Method Usage

Function arguments are separated by a single trailing space after the comma delimiter. This is an example of an acceptable function call for a function that takes three arguments:

threeArguments(1, 2, 3);

Call-time pass by-reference is prohibited. Arguments to be passed by reference must be defined in the function declaration.

For functions whose arguments permit arrays, the function call may include the “array” construct and can be split into multiple lines to improve readability. In these cases, the standards for writing arrays still apply:

threeArguments(array(1, 2, 3), 2, 3);

threeArguments(array(1, 2, 3, ‘Yii’,

$a, $b, $c,

56.44, $d, 500), 2, 3);

Control Statements

If / Else / Elseif

Control statements based on the “if”, “else”, and “elseif” constructs must have a single space before the opening parenthesis of the conditional, and a single space between the closing parenthesis and opening brace.

Within the conditional statements between the parentheses, operators must be separated by spaces for readability. Inner parentheses are encouraged to improve logical grouping of larger conditionals.

The opening brace is written on the same line as the conditional statement. The closing brace is always written on its own line. Any content within the braces must be indented four spaces.

if ($a != 2) {

$a = 2;


For “if” statements that include “elseif” or “else”, the formatting must be as in these examples:

if ($a != 2) {

$a = 2;

} else {

$a = 7;


if ($a != 2) {

$a = 2;

} else if ($a == 3) {

$a = 4;

} else {

$a = 7;


PHP allows for these statements to be written without braces in some circumstances. The coding standard makes no differentiation and all “if”, “elseif”, or “else” statements must use braces.

Use of the “elseif” construct is permitted but highly discouraged in favor of the “else if” combination.


Control statements written with the “switch” construct must have a single space before the opening parenthesis of the conditional statement, and also a single space between the closing parenthesis and the opening brace.

All content within the “switch” statement must be indented four spaces. Content under each “case” statement must be indented an additional four spaces.

switch ($numPeople) {

case 1:


case 2:





The construct “default” may never be omitted from a “switch” statement.

Please note

It is sometimes useful to write a “case” statement which falls through to the next case by not including a “break” or “return”. To distinguish these cases from bugs, such “case” statements must contain the comment “// break intentionally omitted”.

Inline Documentation

Documentation Format

All documentation blocks (“docblocks”) must be compatible with the phpDocumentor format. Describing the phpDocumentor format is beyond the scope of this document. For more information, visit http://phpdoc.org.

All source code file written for the Yii Framework or that operates with the framework must contain a “file-level” docblock at the top of each file and a “class-level” docblock immediately above each class. Below are examples of such docblocks.

The sharp, ‘#’, character should not be used to start comments.


Every file that contains PHP code must have a header block at the top of the file that contains these phpDocumentor tags at a minimum:


* Short description for file


* Long description for file (if any)…


* LICENSE: Some license information


* @copyright 2006 Yii

* @license http://www.gnu.com/license/3_0.txt PHP License 3.0

* @version $Id$

* @since 1.0.0



Every class must have a docblock that contains these phpDocumentor tags at a minimum:


* Short description for class


* Long description for class (if any)…


* @author author name

* @version Release: @package_version@



Every function, including object methods, must have a docblock that contains at a minimum:

  • A description of the function
  • All of the arguments
  • All of the possible return values
  • If a function/method may throw an exception, use “@throws”

Please note

It is not necessary to use the “@access” tag because the access level is already known from the “public”, “private”, or “protected” construct used to declare the function.


* Does something interesting


* @param Place $where Where something interesting takes place

* @param integer $repeat How many times something interesting should happen

* @throws Some_Exception_Class If something interesting cannot happen

* @return Status


public function doSomethingInteresting(Place $where, $repeat = 1)


// implementation…


Require / Include

If a component uses another component, then the using component is responsible for loading the other component. If the use is conditional, then the loading should also be conditional.

The include, include_once, require, and require_once statements should not use parentheses.

Using include, include_once, require, and require_once is acceptable but discouraged in favor for Yii:import();

Errors and Exceptions

The Yii Framework codebase must be E_STRICT compliant. Yii Framework code should not emit PHP warning (E_WARNING, E_USER_WARNING), notice (E_NOTICE, E_USER_NOTICE), or strict (E_STRICT) messages when error_reporting is set to E_ALL | E_STRICT.

See http://www.php.net/errorfunc for information on E_STRICT.

Yii Framework code should not emit PHP errors, if it is reasonably possible. Instead, throw meaningful exceptions. Yii Framework components have Exception class derivatives specifically for this purpose:

class CException extends Exception


class CController_Exception extends CException


class CController_Other_Exception extends CController_Exception


It is considered best practice within framework component code that exceptions are instantiated through the traditional new constructor method.


class Test_Component


public function foo($condition)


if ($condition) {

throw new Component_Exception(

‘Some meaningful exception message’);




Some concern was raised about scripts that incur overhead by loading exception classes that are by definition only used in exceptional cases. When an application’s performance requirements are such that this overhead is an issue, one should use either of two solutions:

  • Load the exception class in a traditional manner, and run the application in an environment that uses a PHP bytecode cache. A bytecode cache reduces the overhead of loading and parsing PHP classes that have been used in the environment earlier.
  • Lazy-load the exception class inside the code block where the exception is thrown. For example:

if ($condition) {

require_once ‘Component_Exception.php’;

throw new Component_Exception(

‘Some meaningful exception message’);


Reasonable care should be taken to avoid throwing exceptions except when genuinely appropriate. In general, if a Yii Framework component is asked to perform a duty that it cannot perform in a certain situation (e.g., illegal input, cannot read requested file), then throwing an exception is a sensible course of action. Conversely, if a component is able to perform its requested duty, despite some variance from expected input, then the component should continue with its work, rather than throw an exception.

Exception best practices

  • Use specific derived exceptions in both throw and catch. See the following two items:
  • Avoid throwing the Exception base class, or other exception superclass. The more specific the exception, the better it communicates to the user what happened.
  • Avoid catching the Exception base class, or other exception superclass. If a try block might encounter more than one type of exception, write a separate catch block for each specific exception, not one catch block for an exception superclass.
  • Some classes may require you to write more than one derived exception class. Write as many exception classes as needed, to distinguish between different types of situations. For example, “invalid argument value” is different from, “you don’t have a needed privilege.” Create different exceptions to identify different cases.
  • Don’t put important diagnostic information only in the text of the exception method. Create methods and members in derived exception classes as needed, to provide information to the catch block. Create an exception constructor method that takes appropriate arguments, and populate the members of the class with those arguments.
  • Don’t silently suppress exceptions and allow execution to continue in an erroneous state. If you catch an exception, either correct the condition or throw a new exception.
  • Keep implementation-specific exceptions isolated to the appropriate layer of your application. For instance, don’t propagate SQLException out of the data layer code and into business layer code.
  • Don’t use exceptions as a mechanism of flow control, or to return valid return values from a function.
  • Clean up resources such as database connections or network connections. PHP does not support a finally block as some programming languages do, so either clean up in the catch blocks, or else design flow control outside the catch block to perform cleanup, and let execution continue after the catch.
  • Use documentation from other languages for other best practices regarding using exceptions. Many of the principles are applicable, regardless of the language.

PHP Error Suppression (@ ) in front of method names, class members and properties is prohibited.