Formatting Guidelines


Over the years Cacti has attempted to adhere to standards in code construction, syntax, style, etc. It has been a very organic grow which has resulted in some mixed styles. Cacti is in the process of moving to PHP Standards Recommendations (PSR) standards.

Initially we are moving towards PSR-2 code syntax standard with the following exceptions:

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


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 ($var == 0) {
} elseif ($var == 1) {
} else {
    $i = 0;

switch Construct

switch ($var) {
    case 0:
        $var = 1;

    case 1:
        $var = 2;

        $var = 3;


while Loop

while ($i < 10) {

for Loop

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

foreach Loop

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


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

Returns a specific user

function user_get($user_id) {
    // code

Returns 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 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.


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_SNMP', 4);

Common Action Types


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.

White space

Always place a single blank line after a control structure unless the following line is an ending brace }. There should be no blank lines at the end of the file, and no spaces at the end of line.

if ($var == 0) {
    $i = 0;

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

Storage Constructs


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

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


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


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


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


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.

function big_array_process(&$big_array) {
    // code

Database Calls

Ensure that you indent your Database calls by a single tab per indentation level and that you break up database calls by the various provisos. A few well defined database queries can be seen in the examples below

$devices = db_fetch_assoc_prepared('SELECT *
  FROM host
  WHERE id = ?',

$vdefs = db_fetch_assoc("SELECT rs.*,
  SUM(CASE WHEN local_graph_id = 0 THEN 1 ELSE 0 END) AS templates,
  SUM(CASE WHEN local_graph_id > 0 THEN 1 ELSE 0 END) AS graphs
  FROM (
    SELECT vd.*, gti.local_graph_id
    FROM vdef AS vd
    LEFT JOIN graph_templates_item AS gti
    ON gti.vdef_id =
    GROUP BY, gti.graph_template_id, gti.local_graph_id
  ) AS rs
  1. Ensure that you use prepared statements as in the first example whenever you can.

  2. If you can not use prepared statements, ensure that you properly escape any database SQL WHERE logic properly.

  3. Always use the term AS to define an alias.

  4. Ensure that your JOINs are either INNER, LEFT, or RIGHT.

  5. Ensure that the ON clause uses table aliases, and that each AND or OR expression is logically organized for easy reading and interpretation.

  6. In your SQL WHERE and SELECT, where fuctions are involved

    1. Ensure that there are spaces between parameter
    2. Ensure operators and variables are separated by spaces


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) 2004-2022 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          |
 | 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.   |
 |                                                   |

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 per PHP DocBlock specifications as follow:

 * 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

Place a space between the @param and @return.

Copyright (c) 2004-2022 The Cacti Group