PHP Style Guide
***************

The following page describes the coding styles adhered to when
contributing to the development of CodeIgniter. There is no
requirement to use these styles in your own CodeIgniter application,
though they are recommended.


Table of Contents
^^^^^^^^^^^^^^^^^

* PHP Style Guide

  * File Format

    * TextMate

    * BBEdit

  * PHP Closing Tag

  * File Naming

  * Class and Method Naming

  * Variable Names

  * Commenting

  * Constants

  * TRUE, FALSE, and NULL

  * Logical Operators

  * Comparing Return Values and Typecasting

  * Debugging Code

  * Whitespace in Files

  * Compatibility

  * One File per Class

  * Whitespace

  * Line Breaks

  * Code Indenting

  * Bracket and Parenthetic Spacing

  * Localized Text

  * Private Methods and Variables

  * PHP Errors

  * Short Open Tags

  * One Statement Per Line

  * Strings

  * SQL Queries

  * Default Function Arguments


File Format
===========

Files should be saved with Unicode (UTF-8) encoding. The BOM should
*not* be used. Unlike UTF-16 and UTF-32, there’s no byte order to
indicate in a UTF-8 encoded file, and the BOM can have a negative side
effect in PHP of sending output, preventing the application from being
able to set its own headers. Unix line endings should be used (LF).

Here is how to apply these settings in some of the more common text
editors. Instructions for your text editor may vary; check your text
editor’s documentation.


TextMate
--------

1. Open the Application Preferences

2. Click Advanced, and then the “Saving” tab

3. In “File Encoding”, select “UTF-8 (recommended)”

4. In “Line Endings”, select “LF (recommended)”

5. *Optional:* Check “Use for existing files as well” if you wish to
   modify the line endings of files you open to your new preference.


BBEdit
------

1. Open the Application Preferences

2. Select “Text Encodings” on the left.

3. In “Default text encoding for new documents”, select “Unicode
   (UTF-8, no BOM)”

4. *Optional:* In “If file’s encoding can’t be guessed, use”, select
   “Unicode (UTF-8, no BOM)”

5. Select “Text Files” on the left.

6. In “Default line breaks”, select “Mac OS X and Unix (LF)”


PHP Closing Tag
===============

The PHP closing tag on a PHP document **?>** is optional to the PHP
parser. However, if used, any whitespace following the closing tag,
whether introduced by the developer, user, or an FTP application, can
cause unwanted output, PHP errors, or if the latter are suppressed,
blank pages. For this reason, all PHP files MUST OMIT the PHP closing
tag and end with a single empty line instead.


File Naming
===========

Class files must be named in a Ucfirst-like manner, while any other
file name (configurations, views, generic scripts, etc.) should be in
all lowercase.

**INCORRECT**:

   somelibrary.php
   someLibrary.php
   SOMELIBRARY.php
   Some_Library.php

   Application_config.php
   Application_Config.php
   applicationConfig.php

**CORRECT**:

   Somelibrary.php
   Some_library.php

   applicationconfig.php
   application_config.php

Furthermore, class file names should match the name of the class
itself. For example, if you have a class named *Myclass*, then its
filename must be **Myclass.php**.


Class and Method Naming
=======================

Class names should always start with an uppercase letter. Multiple
words should be separated with an underscore, and not CamelCased.

**INCORRECT**:

   class superclass
   class SuperClass

**CORRECT**:

   class Super_class

   class Super_class {

           public function __construct()
           {

           }
   }

Class methods should be entirely lowercased and named to clearly
indicate their function, preferably including a verb. Try to avoid
overly long and verbose names. Multiple words should be separated with
an underscore.

**INCORRECT**:

   function fileproperties()               // not descriptive and needs underscore separator
   function fileProperties()               // not descriptive and uses CamelCase
   function getfileproperties()            // Better!  But still missing underscore separator
   function getFileProperties()            // uses CamelCase
   function get_the_file_properties_from_the_file()        // wordy

**CORRECT**:

   function get_file_properties()  // descriptive, underscore separator, and all lowercase letters


Variable Names
==============

The guidelines for variable naming are very similar to those used for
class methods. Variables should contain only lowercase letters, use
underscore separators, and be reasonably named to indicate their
purpose and contents. Very short, non-word variables should only be
used as iterators in for() loops.

**INCORRECT**:

   $j = 'foo';             // single letter variables should only be used in for() loops
   $Str                    // contains uppercase letters
   $bufferedText           // uses CamelCasing, and could be shortened without losing semantic meaning
   $groupid                // multiple words, needs underscore separator
   $name_of_last_city_used // too long

**CORRECT**:

   for ($j = 0; $j < 10; $j++)
   $str
   $buffer
   $group_id
   $last_city


Commenting
==========

In general, code should be commented prolifically. It not only helps
describe the flow and intent of the code for less experienced
programmers, but can prove invaluable when returning to your own code
months down the line. There is not a required format for comments, but
the following are recommended.

DocBlock style comments preceding class, method, and property
declarations so they can be picked up by IDEs:

   /**
    * Super Class
    *
    * @package     Package Name
    * @subpackage  Subpackage
    * @category    Category
    * @author      Author Name
    * @link        http://example.com
    */
   class Super_class {

   /**
    * Encodes string for use in XML
    *
    * @param       string  $str    Input string
    * @return      string
    */
   function xml_encode($str)

   /**
    * Data for class manipulation
    *
    * @var array
    */
   public $data = array();

Use single line comments within code, leaving a blank line between
large comment blocks and code.

   // break up the string by newlines
   $parts = explode("\n", $str);

   // A longer comment that needs to give greater detail on what is
   // occurring and why can use multiple single-line comments.  Try to
   // keep the width reasonable, around 70 characters is the easiest to
   // read.  Don't hesitate to link to permanent external resources
   // that may provide greater detail:
   //
   // http://example.com/information_about_something/in_particular/

   $parts = $this->foo($parts);


Constants
=========

Constants follow the same guidelines as do variables, except constants
should always be fully uppercase. *Always use CodeIgniter constants
when appropriate, i.e. SLASH, LD, RD, PATH_CACHE, etc.*

**INCORRECT**:

   myConstant      // missing underscore separator and not fully uppercase
   N               // no single-letter constants
   S_C_VER         // not descriptive
   $str = str_replace('{foo}', 'bar', $str);       // should use LD and RD constants

**CORRECT**:

   MY_CONSTANT
   NEWLINE
   SUPER_CLASS_VERSION
   $str = str_replace(LD.'foo'.RD, 'bar', $str);


TRUE, FALSE, and NULL
=====================

**TRUE**, **FALSE**, and **NULL** keywords should always be fully
uppercase.

**INCORRECT**:

   if ($foo == true)
   $bar = false;
   function foo($bar = null)

**CORRECT**:

   if ($foo == TRUE)
   $bar = FALSE;
   function foo($bar = NULL)


Logical Operators
=================

Use of the "||" “or” comparison operator is discouraged, as its
clarity on some output devices is low (looking like the number 11, for
instance). "&&" is preferred over "AND" but either are acceptable, and
a space should always precede and follow "!".

**INCORRECT**:

   if ($foo || $bar)
   if ($foo AND $bar)  // okay but not recommended for common syntax highlighting applications
   if (!$foo)
   if (! is_array($foo))

**CORRECT**:

   if ($foo OR $bar)
   if ($foo && $bar) // recommended
   if ( ! $foo)
   if ( ! is_array($foo))


Comparing Return Values and Typecasting
=======================================

Some PHP functions return FALSE on failure, but may also have a valid
return value of “” or 0, which would evaluate to FALSE in loose
comparisons. Be explicit by comparing the variable type when using
these return values in conditionals to ensure the return value is
indeed what you expect, and not a value that has an equivalent loose-
type evaluation.

Use the same stringency in returning and checking your own variables.
Use **===** and **!==** as necessary.

**INCORRECT**:

   // If 'foo' is at the beginning of the string, strpos will return a 0,
   // resulting in this conditional evaluating as TRUE
   if (strpos($str, 'foo') == FALSE)

**CORRECT**:

   if (strpos($str, 'foo') === FALSE)

**INCORRECT**:

   function build_string($str = "")
   {
           if ($str == "") // uh-oh!  What if FALSE or the integer 0 is passed as an argument?
           {

           }
   }

**CORRECT**:

   function build_string($str = "")
   {
           if ($str === "")
           {

           }
   }

See also information regarding typecasting, which can be quite useful.
Typecasting has a slightly different effect which may be desirable.
When casting a variable as a string, for instance, NULL and boolean
FALSE variables become empty strings, 0 (and other numbers) become
strings of digits, and boolean TRUE becomes “1”:

   $str = (string) $str; // cast $str as a string


Debugging Code
==============

Do not leave debugging code in your submissions, even when commented
out. Things such as "var_dump()", "print_r()", "die()"/"exit()" should
not be included in your code unless it serves a specific purpose other
than debugging.


Whitespace in Files
===================

No whitespace can precede the opening PHP tag or follow the closing
PHP tag. Output is buffered, so whitespace in your files can cause
output to begin before CodeIgniter outputs its content, leading to
errors and an inability for CodeIgniter to send proper headers.


Compatibility
=============

CodeIgniter recommends PHP 5.6 or newer to be used, but it should be
compatible with PHP 5.3.7. Your code must either be compatible with
this requirement, provide a suitable fallback, or be an optional
feature that dies quietly without affecting a user’s application.

Additionally, do not use PHP functions that require non-default
libraries to be installed unless your code contains an alternative
method when the function is not available.


One File per Class
==================

Use separate files for each class, unless the classes are *closely
related*. An example of a CodeIgniter file that contains multiple
classes is the Xmlrpc library file.


Whitespace
==========

Use tabs for whitespace in your code, not spaces. This may seem like a
small thing, but using tabs instead of whitespace allows the developer
looking at your code to have indentation at levels that they prefer
and customize in whatever application they use. And as a side benefit,
it results in (slightly) more compact files, storing one tab character
versus, say, four space characters.


Line Breaks
===========

Files must be saved with Unix line breaks. This is more of an issue
for developers who work in Windows, but in any case ensure that your
text editor is setup to save files with Unix line breaks.


Code Indenting
==============

Use Allman style indenting. With the exception of Class declarations,
braces are always placed on a line by themselves, and indented at the
same level as the control statement that “owns” them.

**INCORRECT**:

   function foo($bar) {
           // ...
   }

   foreach ($arr as $key => $val) {
           // ...
   }

   if ($foo == $bar) {
           // ...
   } else {
           // ...
   }

   for ($i = 0; $i < 10; $i++)
           {
           for ($j = 0; $j < 10; $j++)
                   {
                   // ...
                   }
           }

   try {
           // ...
   }
   catch() {
           // ...
   }

**CORRECT**:

   function foo($bar)
   {
           // ...
   }

   foreach ($arr as $key => $val)
   {
           // ...
   }

   if ($foo == $bar)
   {
           // ...
   }
   else
   {
           // ...
   }

   for ($i = 0; $i < 10; $i++)
   {
           for ($j = 0; $j < 10; $j++)
           {
                   // ...
           }
   }

   try
   {
           // ...
   }
   catch()
   {
           // ...
   }


Bracket and Parenthetic Spacing
===============================

In general, parenthesis and brackets should not use any additional
spaces. The exception is that a space should always follow PHP control
structures that accept arguments with parenthesis (declare, do-while,
elseif, for, foreach, if, switch, while), to help distinguish them
from functions and increase readability.

**INCORRECT**:

   $arr[ $foo ] = 'foo';

**CORRECT**:

   $arr[$foo] = 'foo'; // no spaces around array keys

**INCORRECT**:

   function foo ( $bar )
   {

   }

**CORRECT**:

   function foo($bar) // no spaces around parenthesis in function declarations
   {

   }

**INCORRECT**:

   foreach( $query->result() as $row )

**CORRECT**:

   foreach ($query->result() as $row) // single space following PHP control structures, but not in interior parenthesis


Localized Text
==============

CodeIgniter libraries should take advantage of corresponding language
files whenever possible.

**INCORRECT**:

   return "Invalid Selection";

**CORRECT**:

   return $this->lang->line('invalid_selection');


Private Methods and Variables
=============================

Methods and variables that are only accessed internally, such as
utility and helper functions that your public methods use for code
abstraction, should be prefixed with an underscore.

   public function convert_text()
   private function _convert_text()


PHP Errors
==========

Code must run error free and not rely on warnings and notices to be
hidden to meet this requirement. For instance, never access a variable
that you did not set yourself (such as "$_POST" array keys) without
first checking to see that it "isset()".

Make sure that your dev environment has error reporting enabled for
ALL users, and that display_errors is enabled in the PHP environment.
You can check this setting with:

   if (ini_get('display_errors') == 1)
   {
           exit "Enabled";
   }

On some servers where *display_errors* is disabled, and you do not
have the ability to change this in the php.ini, you can often enable
it with:

   ini_set('display_errors', 1);

Note:

  Setting the display_errors setting with "ini_set()" at runtime is
  not identical to having it enabled in the PHP environment. Namely,
  it will not have any effect if the script has fatal errors.


Short Open Tags
===============

Always use full PHP opening tags, in case a server does not have
*short_open_tag* enabled.

**INCORRECT**:

   <? echo $foo; ?>

   <?=$foo?>

**CORRECT**:

   <?php echo $foo; ?>

Note:

  PHP 5.4 will always have the **<?=** tag available.


One Statement Per Line
======================

Never combine statements on one line.

**INCORRECT**:

   $foo = 'this'; $bar = 'that'; $bat = str_replace($foo, $bar, $bag);

**CORRECT**:

   $foo = 'this';
   $bar = 'that';
   $bat = str_replace($foo, $bar, $bag);


Strings
=======

Always use single quoted strings unless you need variables parsed, and
in cases where you do need variables parsed, use braces to prevent
greedy token parsing. You may also use double-quoted strings if the
string contains single quotes, so you do not have to use escape
characters.

**INCORRECT**:

   "My String"                                     // no variable parsing, so no use for double quotes
   "My string $foo"                                // needs braces
   'SELECT foo FROM bar WHERE baz = \'bag\''       // ugly

**CORRECT**:

   'My String'
   "My string {$foo}"
   "SELECT foo FROM bar WHERE baz = 'bag'"


SQL Queries
===========

SQL keywords are always capitalized: SELECT, INSERT, UPDATE, WHERE,
AS, JOIN, ON, IN, etc.

Break up long queries into multiple lines for legibility, preferably
breaking for each clause.

**INCORRECT**:

   // keywords are lowercase and query is too long for
   // a single line (... indicates continuation of line)
   $query = $this->db->query("select foo, bar, baz, foofoo, foobar as raboof, foobaz from exp_pre_email_addresses
   ...where foo != 'oof' and baz != 'zab' order by foobaz limit 5, 100");

**CORRECT**:

   $query = $this->db->query("SELECT foo, bar, baz, foofoo, foobar AS raboof, foobaz
                                   FROM exp_pre_email_addresses
                                   WHERE foo != 'oof'
                                   AND baz != 'zab'
                                   ORDER BY foobaz
                                   LIMIT 5, 100");


Default Function Arguments
==========================

Whenever appropriate, provide function argument defaults, which helps
prevent PHP errors with mistaken calls and provides common fallback
values which can save a few lines of code. Example:

   function foo($bar = '', $baz = FALSE)
