user_guide_src/source/general/styleguide.rst - code-igniter-v3-giggi - Gitiles

 ###############
 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.

 .. contents:: Table of Contents

 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
 ''''''''

 #. Open the Application Preferences
 #. Click Advanced, and then the "Saving" tab
 #. In "File Encoding", select "UTF-8 (recommended)"
 #. In "Line Endings", select "LF (recommended)"
 #. *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
 ''''''

 #. Open the Application Preferences
 #. Select "Text Encodings" on the left.
 #. In "Default text encoding for new documents", select "Unicode (UTF-8,
    no BOM)"
 #. *Optional:* In "If file's encoding can't be guessed, use", select
    "Unicode (UTF-8, no BOM)"
 #. Select "Text Files" on the left.
 #. 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 <http://manual.phpdoc.org/HTMLSmartyConverter/HandS/phpDocumentor/tutorial_phpDocumentor.howto.pkg.html#basics.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
 <http://php.net/manual/en/language.types.type-juggling.php#language.types.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
 	<http://php.net/manual/en/errorfunc.configuration.php#ini.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)
	###############
	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.

	.. contents:: Table of Contents

	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
	''''''''

	#. Open the Application Preferences
	#. Click Advanced, and then the "Saving" tab
	#. In "File Encoding", select "UTF-8 (recommended)"
	#. In "Line Endings", select "LF (recommended)"
	#. 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
	''''''

	#. Open the Application Preferences
	#. Select "Text Encodings" on the left.
	#. In "Default text encoding for new documents", select "Unicode (UTF-8,
	no BOM)"
	#. Optional: In "If file's encoding can't be guessed, use", select
	"Unicode (UTF-8, no BOM)"
	#. Select "Text Files" on the left.
	#. 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 <http://manual.phpdoc.org/HTMLSmartyConverter/HandS/phpDocumentor/tutorial_phpDocumentor.howto.pkg.html#basics.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
	<http://php.net/manual/en/language.types.type-juggling.php#language.types.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
	<http://php.net/manual/en/errorfunc.configuration.php#ini.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)