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$Id: CODING_STANDARDS.txt,v 1.3 2005/06/20 12:57:39 demian Exp $
=========================
Seagull Coding Standards
=========================
Copied and slightly adapted from the Horde project
Authors: Jon Parise, Chuck Hagenbuch
Indenting
=========
Use an indent of 4 spaces, with no tabs.
Control Structures
==================
These include ``if``, ``for``, ``while``, ``switch``, etc. Here is an example
``if`` statement, since it is the most complicated of them::
if ((condition1) || (condition2)) {
action1;
} elseif ((condition3) && (condition4)) {
action2;
} else {
defaultaction;
}
Multi-line if conditions are braced this way::
if ((condition1) || (condition2) || (condition3) ||
(condition4)) {
action1;
}
Control statements should have one space between the control keyword and
opening parenthesis, to distinguish them from function calls.
Do not omit the curly braces under any circumstance.
...
For switch statements::
switch (condition) {
case 1:
action1;
break;
case 2:
action2;
break;
default:
defaultaction;
break;
}
Function Calls
==============
Functions should be called with no spaces between the function name, the
opening parenthesis, and the first parameter; spaces between commas and each
parameter, and no space between the last parameter, the closing parenthesis,
and the semicolon. Here's an example::
$var = foo($bar, $baz, $quux);
As displayed above, there should be one space on either side of an equals sign
used to assign the return value of a function to a variable. In the case of a
block of related assignments, more space may be inserted to promote
readability::
$short = foo($bar);
$longvariable = foo($baz);
If assigning a reference to a variable, place the ampersand next to the
referenced object, not the equal sign::
$reference = &$foo;
$reference = &foo();
Function Definitions
====================
Function declaractions follow the "one true brace" convention::
function fooFunction($arg1, $arg2 = '')
{
if (condition) {
statement;
}
return $val;
}
Arguments with default values go at the end of the argument list. Always
attempt to return a meaningful value from a function if one is appropriate.
Functions used only in the current script/class (e.g. private member methods)
should begin with a ``_`` character (e.g. ``_exampleLibrary``). This helps
distinguish these private function calls from other, public function calls.
Comments
========
Inline documentation for classes should follow the `Javadoc convention`.
.. Javadoc convention: http://java.sun.com/products/jdk/javadoc/writingdoccomments/index.html
Quick example for private variable definition for Seagull::
/**
* Variable description.
*
* @var datatype $variable name
*/
Quick example function definition for Seagull::
/**
* The description of the function goes here.
*
* @access [public | private]
*
* @param datatype $variablename Description of variable.
* @param datatype $variable2name Description of variable2.
* ...
* [Insert 2 spaces after the longest $variable definition, and then line
* up all descriptions with this description]
*
* @return datatype Description of return value.
* [Once again, insert 2 spaces after the datatype, and line up all
* subsequent lines, if any, with this character.]
*
* @abstract [Only if necessary]
*/
Including Code
==============
If you are including a class, function library, or anything else which would
cause a parse error if included twice, always use `include_once`. This will
ensure that no matter how many factory methods we use or how much dynamic
inclusion we do, the library will only be included once.
If you are including a static filename, such as a conf file or a template that
is *always* used, use `require`.
If you are dynamically including a filename, or want the code to only be used
conditionally (an optional template), use `include`.
.. include_once: http://www.php.net/manual/en/function.include-once.php
.. require: http://www.php.net/manual/en/function.require.php
.. include: http://www.php.net/manual/en/function.include.php
PHP Code Tags
=============
Always use ``<?php ?>`` to delimit PHP code, not the ``<? ?>`` shorthand.
This is required for PEAR compliance and is also the most portable way to
include PHP code on differing operating systems and setups.
In templates, make sure to use this as well (``<?php echo $varname ?>``), as
the shortcut version (``<?= $var ?>``) does not work with `short_open_tag`
turned off.
.. short_open_tag: http://www.php.net/manual/en/configuration.directives.php#ini.short-open-tag
Header Comment Blocks
=====================
TODO
There's no hard rule to determine when a new code contributer should be added
to the list of authors for a given source file. In general, their changes
should fall into the "substantial" category (meaning somewhere around 10% to
20% of code changes). Exceptions could be made for rewriting functions or
contributing new logic.
Simple code reorganization or bug fixes would not justify the addition of a
new individual to the list of authors.
Example URLs
============
Use ``example.com`` for all example URLs, per `RFC 2606`.
.. RFC 2606: http://www.faqs.org/rfcs/rfc2606.html
php.ini settings
================
All Seagull code should work with `register_globals` disabled. This means
using ``$COOKIE``, ``$SESSION``, ``$SERVER`` and ``$ENV`` to access all
cookie, session, server and environment data, respectively.
All Seagull code should work with `errorreporting` = E_ALL. Failure to do so
would result in ugly output, error logs getting filled with lots of warning
messages, or even downright broken scripts.
XHTML 1.0 Compliance
====================
All tag names and parameters must be lower case including javascript event
handlers::
<font color="#FFFFFF">...</font>
<a href="http://example.com" onmouseover="status=''" onmouseout="status=''">...</a>
All tag parameters must be of a valid parameter="value" form (numeric values
must also be surrounded by quotes). For parameters that had no value in HTML,
the parameter name is the value. For example::
<input type="checkbox" checked="checked">
<select name="example">
<option selected="selected" value="1">Example</option>
</select>
<td nowrap="nowrap">Example</td>
All tags must be properly closed. Tags where closing is forbidden must end
with a space and a slash::
<br />
<hr />
<img src="example.gif" alt="Example" />
<input type="submit" value="Example" />
All form definitions must be on their own line and either fully defined within
a ``<td></td>`` pair or be outside table tags. Forms must also always have an
action parameter::
<form method="post" action="http://example.com/example.cgi">
<table>
<tr><td>example</td></tr>
</table>
</form>
<table>
<tr><td>
<form action="javascript:void(0)" onsubmit="return false;">
</form>
</td></tr>
</table>
All JavaScript tags must have a valid language and type parameters::
<script language="JavaScript" type="text/javascript">
<!--
...
// -->
</script>
Nothing may appear after ``</html>``, therefore include any common footers
after all other output.
All images must have an ``alt`` attribute::
<img src="example.gif" alt="<?php echo ("Example") ?>" />
File Naming Conventions
===========================
Use the PEAR naming standard which observes the following rules:
MyClass.php // any file with a class definition
file.php // any file with procedural code
Follow the Java one-class-per-file convention unless it is considerably
inconvient to do so, ie, for performance reasons.
Note the psuedo name-spacing convention to ensure class name uniqueness:
Foo/Bar/Baz.php // filename
class Foo_Bar_Baz {} // classname
This convention is especially important for all files in your lib directory.
See the PEAR repository for many examples.
Database Naming Conventions
===========================
All database tables used by Seagull applications need to
make sure that their table and field names work in all databases. Many
databases reserve words like 'uid', 'user', etc. for internal use, and forbid
words that are SQL keywords (SELECT, WHERE, etc.). Also, all table and field
names should be lowercase, with underscores ('_') to separate words, to avoid
case sensitivity issues. Also, all SQL keywords should be uppercase, here is
an example:
SELECT foo_id, foo_name FROM bar WHERE foo_id < $x
Other general guidelines: Table names should be singular (faq); field names
should be also be singular (username).
Foreign Key Naming Conventions
==============================
If table_foo.field_foo references table_bar.field_bar, write the constraint
as follows:
ALTER TABLE table_foo ADD CONSTRAINT FK_table_bar_field_bar FOREIGN KEY (field_foo)
REFERENCES table_bar (field_bar) on DELETE CASCADE;
Regular Expression Use
======================
Always use the `preg` functions if possible instead of `ereg` (and
`preg_split()` instead of `split()`); they are included in PHP by default
and much more efficient and much faster than `ereg`.
**NEVER** use a regular expression to match or replace a static string.
`explode()` (in place of `split()`), `str_replace()`, `strpos()`, or
`strtr()` do the job much more efficiently.
.. preg: http://www.php.net/manual/en/ref.pcre.php
.. ereg: http://www.php.net/manual/en/ref.regex.php
.. pregsplit(): http://www.php.net/manual/en/function.preg-split.php
.. split(): http://www.php.net/manual/en/function.split.php
.. explode(): http://www.php.net/manual/en/function.explode.php
.. strreplace(): http://www.php.net/manual/en/function.str-replace.php
.. strpos(): http://www.php.net/manual/en/function.strpos.php
.. strtr(): http://www.php.net/manual/en/function.strtr.php
Parameter Passing
=================
Objects should be passed by reference. Everything else, including arrays,
should be passed by value wherever semantically possible.
This practice takes full advantage of reference counting.
Long Lines
==========
Wrap lines at 80 characters, including comments, unless this severely impacts
the clarity of the code. Always wrap comments.
Line Breaks
===========
Only use UNIX style of linebreak (``\n``), not Windows/DOS/Mac style
(``\r\n``).
Using vim, to convert from DOS style type::
:set ff=unix
Using vi, to convert from DOS style type::
:g/^M/s///g
(Note that the ``^M`` is a control character, and to reproduce it when you
type in the vi command you have to pad it first using the special ``^V``
character.)
Private Variables
=================
Variables used exclusively within a class should begin with a underscore ('_')
character. An example class variable definition: ``var $_variablename;``
Array Definitions
=================
When defining arrays, or nested arrays, use the following format, where
indentation is noted via the closing parenthesis characters::
$arrayname['index'] = array(
'name1' => 'value1',
'name2' => array(
'subname1' => 'subvalue1',
'subname2' => 'subvalue2'
)
);
The only exception should be for empty arrays, which may be written on a
single line such as::
$arrayname['index'] = array();
Existence checking
==================
Often you'll need to check whether or not a variable or property exists.
There are several cases here:
a. If you need to know if a variable exists at all and is not ``null``, use
`isset()`::
// Check to see if $param is defined.
if (isset($param)) {
// $param may be false, but it's there.
}
b. If you need to know if a variable exists AND has a non-empty value (not
``null``, 0, ``false``, empty string or undefined), use !`empty()`::
// Make sure that $answer exists, is not an empty string, and is
// not 0:
if (!empty($answer)) {
// $answer has some non-false content.
} else {
// (bool)$answer would be false.
}
As pointed out in the comment of the else clause, `empty()` essentially does
the same check as `isset()` -- is this variable defined in the current scope?
-- and then, if it is, returns what the variable would evaluate to as a
boolean. This means that 0, while potentially valid input, is "empty" - so if
0 is valid data for your case, don't use !`empty()`.
c. If you know you are working with a mixed variable then using just
`isset()` and `empty()` could cause unexpected results, for example if
testing for a key and the variable is actually a string::
$foo = 'bar';
if (isset($foo['somekey'])) {
// This will evaluate to TRUE!
}
If you know that there is a possibility of a mixed type variable the solution
in this case would be to add an `is_array()` check in the ``if()`` statement.
d. Use `array_key_exists()` when you want to check if an array key is defined
even if it has a value of ``null``::
// Make sure we have a charset parameter. Value could also be null.
if (!array_key_exists('charset', $params)) {
// ...
}
Please note that `array_key_exists()` is a performance hit (25%-100%) and
should only be used when necessary. Instead try to use !`empty()` or
`isset()` instead.
.. isset(): http://www.php.net/manual/en/function.isset.php
.. empty(): http://www.php.net/manual/en/function.empty.php
.. isarray(): http://www.php.net/manual/en/function.is-array.php
.. array_key_exists(): http://www.php.net/manual/en/function.array-key-exists.php
Quotes
======
You should always use single quote (') characters around strings, except where
double quote (") characters are required. All literal strings should be in
single quotes. A comparison of single and double quote usage follows:
Single Quotes:
* Variables in the string are not parsed or expanded.
* New line symbols can be included as literal line ends (not recommended).
* To include a single quote character, escape it with a ``\`` (backslash)
character, as in: ``echo 'Here\'s an example';``
* To specify a ``\`` (backslash) character, double it: ``echo 'c:\\temp';``
Double Quotes:
* Parses and expands variables in the string.
* Uses advanced (`sprintf`-style) escape sequences like ``\n``, ``\$``,
``\t``, etc.
* Should be used in the gettext shortcut ``("")`` format.
* Use with care, as many correct looking strings are really invalid.
The following are all incorrect::
echo "Today is the $date['day'] of $date['month']"
$SESSION[index] = $SESSION["oldindex"];
.. sprintf: http://www.php.net/sprintf
define()
========
Surprisingly enough, `define()` is a somewhat slow function in PHP (as of PHP
4.3.x) so excessive use is discouraged.
Using `define()` in classes should be OK - we will sacrifice a tiny bit of
speed for readability of code. For anything else, use your best judgment.
Additionally, every constant should be prefixed with ``SGL``, its package
name, or the application name.
.. define(): http://www.php.net/manual/en/function.define.php
Optimizations
=============
The following optimizations should be used, if possible:
Loops
-----
Make sure that you do not continue to define the same variable within a
loop. Instead, declare the variable a single time before the loop is run.
Preferred PHP Conventions
=========================
Instead of file_exists() use is_file(), the former returns true for directories
which can be misleading.
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