WebSVN – MLAB – Rev 317 – Blame – /Forum/docs/codingstandards.htm

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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">

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<HTML><HEAD><TITLE>phpBB Coding Standard Guidelines</TITLE>

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<META content="text/html; charset=windows-1252" http-equiv=Content-Type>

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<META content="MSHTML 5.00.2920.0" name=GENERATOR></HEAD>

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<BODY aLink=#cccccc bgColor=#ffffff link=#0000ff text=#000000

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vLink=#0000ff><A name=top></A>

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<H2>phpBB Coding Standard Guidelines</H2>Comments or suggestions? email <A

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href="mailto:nate@phpbb.com">nate@phpbb.com</A> <A

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href="#editor">Editor

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Settings</A> <A

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href="#naming">Naming

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Conventions</A> <A

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href="#layout">Code Layout</A> <A

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href="#general">General

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Guidelines</A> <A name=editor></A><A

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href="#top">top</A>

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<H3>Editor Settings</H3>

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Tabs vs Spaces: In order to make this as simple as possible, we will

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be using tabs, not spaces. Feel free to set how many spaces your editor uses

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when it displays tabs, but make sure that when you save the file,

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it's saving tabs and not spaces. This way, we can each have the code be

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displayed the way we like it, without breaking the layout of the actual files.

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Linefeeds: Ensure that your editor is saving files in the UNIX format.

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This means lines are terminated with a newline, not with a CR/LF combo as they

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are on Win32, or whatever the Mac uses. Any decent Win32 editor should be able

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to do this, but it might not always be the default. Know your editor. If you

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want advice on Windows text editors, just ask one of the developers. Some of

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them do their editing on Win32. <A name=naming></A><A

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href="#top">top</A>

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<H3>Naming Conventions</H3>

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We will not be using any form of hungarian notation in our naming

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conventions. Many of us believe that hungarian naming is one of the primary code

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obfuscation techniques currently in use. 

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Variable Names: Variable names should be in all lowercase, with words

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separated by an underscore.     Example: <CODE><FONT

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size=+1>$current_user</CODE> is right, but <CODE><FONT

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size=+1>$currentuser</CODE> and <CODE><FONT

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size=+1>$currentUser</CODE> are not. Names should be descriptive,

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but concise. We don't want huge sentences as our variable names, but typing an

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extra couple of characters is always better than wondering what exactly a

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certain variable is for. 

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Loop Indices: The only situation where a one-character variable

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name is allowed is when it's the index for some looping construct. In this case,

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the index of the outer loop should always be $i. If there's a loop inside that

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loop, its index should be $j, followed by $k, and so on. If the loop is being

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indexed by some already-existing variable with a meaningful name, this guideline

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does not apply.     Example: <PRE>

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for ($i = 0; $i < $outer_size; $i++)

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{

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for ($j = 0; $j < $inner_size; $j++)

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{

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foo($i, $j);

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}

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} </PRE>

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Function Names: Functions should also be named descriptively. We're

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not programming in C here, we don't want to write functions called things like

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"stristr()". Again, all lower-case names with words separated by a single

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underscore character. Function names should preferably have a verb in them

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somewhere. Good function names are <CODE><FONT

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size=+1>print_login_status()</CODE>, <CODE><FONT

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size=+1>get_user_data()</CODE>, etc.. 

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Function Arguments: Arguments are subject to the same guidelines as

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variable names. We don't want a bunch of functions like: <CODE><FONT

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size=+1>do_stuff($a, $b, $c)</CODE>. In most cases, we'd like to be able

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to tell how to use a function by just looking at its declaration. 

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Summary: The basic philosophy here is to not hurt code clarity for the

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sake of laziness. This has to be balanced by a little bit of common sense,

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though; <CODE>print_login_status_for_a_given_user()</CODE>

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goes too far, for example -- that function would be better named <CODE><FONT

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size=+1>print_user_login_status()</CODE> , or just <CODE><FONT

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size=+1>print_login_status()</CODE>. <A name=layout></A><A

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href="#top">top</A>

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<H3>Code Layout</H3>

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Standard header for new files: Here a template of the header that must

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be included at the start of all phpBB files: <PRE>

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/***************************************************************************

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filename.php

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-------------------

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begin : Sat June 17 2000

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email : support@phpBB.com

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$Id: codingstandards.htm,v 1.3 2001/06/09 21:00:12 natec Exp $

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***************************************************************************/

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/***************************************************************************

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*

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* This program is free software; you can redistribute it and/or modify

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* it under the terms of the GNU General Public License as published by

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* the Free Software Foundation; either version 2 of the License, or

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* (at your option) any later version.

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*

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***************************************************************************/

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</PRE>

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Always include the braces: This is another case of being too lazy to

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type 2 extra characters causing problems with code clarity. Even if the body of

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some construct is only one line long, do not drop the braces. Just don't.

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    Examples:<PRE>

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/* These are all wrong. */

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if (condition) do_stuff();

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if (condition)

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do_stuff();

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while (condition)

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do_stuff();

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for ($i = 0; $i < size; $i++)

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do_stuff($i);

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/* These are right. */

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if (condition)

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{

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do_stuff();

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}

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while (condition)

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{

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do_stuff();

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}

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for ($i = 0; $i < size; $i++)

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{

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do_stuff();

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}

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</PRE>

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Where to put the braces: This one is a bit of a holy war, but we're

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going to use a style that can be summed up in one sentence: Braces always go on

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their own line. The closing brace should also always be at the same column as

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the corresponding opening brace.    Examples:<PRE>

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if (condition)

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{

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while (condition2)

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{

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...

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}

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}

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else

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{

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...

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}

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for ($i = 0; $i < $size; $i++)

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{

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...

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}

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while (condition)

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{

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...

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}

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function do_stuff()

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{

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...

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}

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</PRE>

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Use spaces between tokens: This is another simple, easy step that

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helps keep code readable without much effort. Whenever you write an assignment,

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expression, etc.. Always leave one space between the tokens. Basically,

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write code as if it was English. Put spaces between variable names and

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operators. Don't put spaces just after an opening bracket or before a closing

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bracket. Don't put spaces just before a comma or a semicolon. This is best shown

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with a few examples.    Examples:<PRE>

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/* Each pair shows the wrong way followed by the right way. */

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$i=0;

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$i = 0;

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if($i<7) ...

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if ($i < 7) ...

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if ( ($i < 7)&&($j > 8) ) ...

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if (($i < 7) && ($j > 8)) ...

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do_stuff( $i, "foo", $b );

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do_stuff($i, "foo", $b);

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for($i=0; $i<$size; $i++) ...

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for($i = 0; $i < $size; $i++) ...

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$i=($j < $size)?0:1;

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$i = ($j < $size) ? 0 : 1;

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</PRE>

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Operator precedence: Do you know the exact precedence of all the

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operators in PHP? Neither do I. Don't guess. Always make it obvious by using

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brackets to force the precedence of an equation so you know what it does.

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    Examples:<PRE>

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/* what's the result? who knows. */

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$bool = ($i < 7 && $j > 8 || $k == 4);

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/* now you can be certain what I'm doing here. */

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$bool = (($i < 7) && (($j < 8) || ($k == 4)))

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</PRE>

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SQL code layout: Since we'll all be using different editor settings,

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don't try to do anything complex like aligning columns in SQL code. Do, however,

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break statements onto their own lines. Here's a sample of how SQL code should

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look. Note where the lines break, the capitalization, and the use of brackets.

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    Examples:<PRE>

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SELECT field1 AS something, field2, field3

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FROM table a, table b

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WHERE (this = that) AND (this2 = that2)

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</PRE>

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SQL insert statements: SQL INSERT statements can be written in two

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different ways. Either you specify explicitly the columns being inserted, or

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you rely on knowing the order of the columns in the database and do not

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specify them. We want to use the former approach, where it is explicitly

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stated whcih columns are being inserted. This means our application-level code

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will not depend on the order of the fields in the database, and will not be broken

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if we add additional fields (unless they're specified as NOT NULL, of course).

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    Examples:<PRE>

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# This is not what we want.

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INSERT INTO mytable

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VALUES ('something', 1, 'else')

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# This is correct.

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INSERT INTO mytable (column1, column2, column3)

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VALUES ('something', 1, 'else')

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</PRE>

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 <A name=general></A><A

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href="#top">top</A>

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<H3>General Guidelines</H3>

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Quoting strings: There are two different ways to quote strings in PHP

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- either with single quotes or with double quotes. The main difference is that

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the parser does variable interpolation in double-quoted strings, but not in

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single quoted strings. Because of this, you should always use single

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quotes unless you specifically need variable interpolation to be done on

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that string. This way, we can save the parser the trouble of parsing a bunch of

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strings where no interpolation needs to be done. Also, if you are using a string

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variable as part of a function call, you do not need to enclose that variable in

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quotes. Again, this will just make unnecessary work for the parser. Note,

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however, that nearly all of the escape sequences that exist for double-quoted

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strings will not work with single-quoted strings. Be careful, and feel free to

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break this guideline if it's making your code harder to read.

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    Examples:<PRE>

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/* wrong */

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$str = "This is a really long string with no variables for the parser to find.";

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do_stuff("$str");

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/* right */

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$str = 'This is a really long string with no variables for the parser to find.';

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do_stuff($str);

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</PRE>

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Associative array keys: In PHP, it's legal to use a literal string as

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a key to an associative array without quoting that string. We don't want to do

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this -- the string should always be quoted to avoid confusion. Note that this is

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only when we're using a literal, not when we're using a variable.

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    Examples:<PRE>

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/* wrong */

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$foo = $assoc_array[blah];

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/* right */

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$foo = $assoc_array['blah'];

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</PRE>

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Comments: Each function should be preceded by a comment that tells a

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programmer everything they need to know to use that function. The meaning of

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every parameter, the expected input, and the output are required as a minimal

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comment. The function's behaviour in error conditions (and what those error

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conditions are) should also be present. Nobody should have to look at the actual

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source of a function in order to be able to call it with confidence in their own

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code. In addition, commenting any tricky, obscure, or otherwise

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not-immediately-obvious code is clearly something we should be doing. Especially

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important to document are any assumptions your code makes, or preconditions for

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its proper operation. Any one of the developers should be able to look at any

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part of the application and figure out what's going on in a reasonable amount of

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time. 

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Magic numbers: Don't use them. Use named constants for any literal

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value other than obvious special cases. Basically, it's OK to check if an array

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has 0 elements by using the literal 0. It's not OK to assign some special

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meaning to a number and then use it everywhere as a literal. This hurts

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readability AND maintainability. Included in this guideline is that we should be

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using the constants TRUE and FALSE in place of the literals 1 and 0 -- even

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though they have the same values, it's more obvious what the actual logic is

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when you use the named constants. 

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Shortcut operators: The only shortcut operators that cause readability

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problems are the shortcut increment ($i++) and decrement ($j--) operators. These

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operators should not be used as part of an expression. They can, however, be

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used on their own line. Using them in expressions is just not worth the

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headaches when debugging.    Examples:<PRE>

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/* wrong */

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$array[++$i] = $j;

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$array[$i++] = $k;

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/* right */

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$i++;

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$array[$i] = $j;

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$array[$i] = $k;

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$i++;

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</PRE>

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Inline conditionals: Inline conditionals should only be used to do

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very simple things. Preferably, they will only be used to do assignments, and

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not for function calls or anything complex at all. They can be harmful to

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readability if used incorrectly, so don't fall in love with saving typing by

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using them.    Examples:<PRE>

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/* Bad place to use them */

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(($i < $size) && ($j > $size)) ? do_stuff($foo) : do_stuff($bar);

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/* OK place to use them */

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$min = ($i < $j) ? $i : $j;

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</PRE>

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Don't use uninitialized variables. for phpBB 2, we intend to use a

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higher level of run-time error reporting. This will mean that the use of an

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uninitialized variable will be reported as an error. This will come up most

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often when checking which HTML form variables were passed. These errors can be

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avoided by using the built-in isset() function to check whether a variable has

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been set.    Examples:<PRE>

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/* Old way */

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if ($forum) ...

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/* New way */

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if (isset($forum)) ...

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</PRE>

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