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Formatting Guidlines

All style guidelines should be followed exactly as shown in these examples unless indicated otherwise.

Indenting

Very simply, always use tabs to indent rather than spaces. Tab stops should be set to 4 spaces.

Below are the vim rules to accomplish this:

set expandtab
set shiftwidth=4
set softtabstop=4
set tabstop=4

Control Structures

Use the following style guidelines for control structures.

if/elseif/else Construct

if ($var == 0) {
	$i++;
}else if ($var == 1) {
	$i--;
}else{
	$i = 0;
}

switch Construct

switch ($var) {
	case 0:
		$var = 1;
		break;
	case 1:
		$var = 2;
		break;
	default:
		$var = 3;
		break;
}

while Loop

while ($i < 10) {
	$i++;
}

for Loop

for ($i = 0; $i < 10; $i++) {
	$var *= 6;
}

foreach Loop

foreach ($array as $key => $value) {
	echo "$key = $value\n";
}

Naming

General Function Naming

All function names should begin with an identifier (see below) and end with an action. The identifier should generally be derived from the name of the file which the function resides.

Returns all users

function user_list() {
	// code
}

Return a specific user

function user_get($user_id) {
	// code
}

Return the total number of graphs

function graph_total_get() {
	// code
}

Returns a specific graph title

function graph_title_get() {
	// code
}

Constant Naming

Constants should always be in all capital letters. In most cases, they begin with some identifier. The name should be verbose enough that it describes exactly what the constant represents. Below is the general structure of the name.

[identifer]_[type]_[value]

Supported graph rendering file types

define('GRAPH_IMAGE_TYPE_PNG', 1);
define('GRAPH_IMAGE_TYPE_GIF', 2);

Data input types for data sources

define('DATA_INPUT_TYPE_NONE', 1);
define('DATA_INPUT_TYPE_DATA_QUERY', 2);
define('DATA_INPUT_TYPE_SCRIPT', 3);
define('DATA_INPUT_TYPE_SNMP', 4);

Common Action Types

  • list - an array of one or more items
  • get - an array with one item or a single value (such as an integer or string)
  • remove - some data is to be removed from the database
  • update - some pre-existing data is to be updated
  • insert - some new data to be saved
  • print - information will be echoed to the screen/browser
  • generate - data will be generated and returned
  • format - data will be passed in, formatted, and then returned

Formatting

Argument Spacing

Always include a single space after each argument in a list except for the last one.

function log_insert($facility, $severity, $message) {
	// code
}
log_insert(LOG_FACILITY_LOCAL0, LOG_LEVEL_WARNING, 'test message');

As a general rule of thumb, it is ok to include additional spaces where necessary to improve code readability. The key here is that writing readable code always takes priority.

Vertical Whitespace

Always place a single blank line after a control structure unless the following line is an ending brace (}) or is the last line in the file.

if ($var == 0) {
	$i = 0;
}
 
if ($i == 0) {
	$i *= 2;
}
if ($var ==0) {
	if ($i == 2) {
		$i++;
	}
}

Storage Constructs

Constants

Always use constants in place of numbers to represent static values. Instead of doing:

if ($poller_verbosity == 2) {
	// code
}

Do:

if ($poller_verbosity == POLLER_VERBOSITY_LOW) {
	// code
}

Variables

Allocating memory for a variable consumes resources. Only declare a variable if it is referenced more than once throughout the code. Instead of doing:

$num_devices = device_total_num_get();
 
if ($num_devices > 0) {
	// code
}

Do:

if (device_total_num_get() > 0) {
	// code
}

Global Variables

Certain situations warrant creating a single variable that is to be referenced by multiple functions. Do not rely on PHP's global keyword since it creates the possibility of name space collisions. Instead, create a wrapper function that brings the variable into a global scope and returns a new copy to any function that needs to use it.

$graph_unit_exponent_values = array('-18' => 'a - atto', '-15' => 'f - femto', ...);
 
function graph_unit_exponent_values_list() {
	global $graph_unit_exponent_values;
 
	return $graph_unit_exponent_values;
}
 
function graph_unit_exponent_values_print() {
	foreach (graph_unit_exponent_values_list() as $power => $unit) {
		// code
	}
}

References

Copying around large arrays in PHP can be an expensive operation. Be sure to return or pass arrays by reference when data corruption is not a huge concern. Keep in mind that call time pass by reference is deprecated in PHP.

function &big_array_list() {
	// code
}
function big_array_process(&$big_array) {
	// code
}

Comments

The key to being a respectable coder is to write clear, concise code and to use comments everywhere.

Whole Line Comments

All single and multi-line comments should follow the C-style syntax.

/* this determines if $i is equal to 0 */
if ($i == 0) {
	// code
}
/* this is an extra long comment that deserves to be
 * split up into multiple lines */
if ($i == 0) {
	// code
}

End of Line Comments

Shorter comments that follow a line of code should use the familiar // style.

$var = 0; // assign 0 to $var

File Header Comments

All code related files must contain the following notice at the beginning of the file.

/*
 +-------------------------------------------------------------------------+
 | Copyright (C) 2004-2010 The Cacti Group                                 |
 |                                                                         |
 | This program is free software; you can redistribute it and/or           |
 | modify it under the terms of the GNU General Public License             |
 | as published by the Free Software Foundation; either version 2          |
 | of the License, or (at your option) any later version.                  |
 |                                                                         |
 | This program is distributed in the hope that it will be useful,         |
 | but WITHOUT ANY WARRANTY; without even the implied warranty of          |
 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the           |
 | GNU General Public License for more details.                            |
 +-------------------------------------------------------------------------+
 | Cacti: The Complete RRDTool-based Graphing Solution                     |
 +-------------------------------------------------------------------------+
 | This code is designed, written, and maintained by the Cacti Group. See  |
 | about.php and/or the AUTHORS file for specific developer information.   |
 +-------------------------------------------------------------------------+
 | http://www.cacti.net/                                                   |
 +-------------------------------------------------------------------------+
*/

Function Comments

All functions must be preceded by a comment describing the purpose, argument list, and return type of the function. It should be formatted as such:

/**
 * Makes a connection to the database server
 *
 * Given a set of login credentials, an attempt is made to establish a persistent database connection.
 * If the attempt fails, script execution will halt with an error.
 *
 * @param string $host the hostname of the database server, 'localhost' if the database server is running
 *   on this machine
 * @param string $user the username to connect to the database server as
 * @param string $pass the password to connect to the database server with
 * @param string $db_name the name of the database to connect to
 * @param string $db_type the type of database server to connect to, only 'mysql' is currently supported
 * @param int $retries the number a time the server should attempt to connect before failing
 * @return bool true if successful, false otherwise
 */

See phpDocumentor's Manual for additional functionality that can be included in function comments.






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