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This document explains the naming convention meant to be used withdynamic and/or weakly typed languages (as defined inthe TypingQuadrant on the Cunningham Wiki) such as PHP, Javascript, Perl, and Bash.

The idea behind the coding convention is that a developer should be abletosee when something is wrong. Either when something from anotherscope is used without validation (parameters in public methods, forinstance) or when a certain type is addressed as though it were anothertype.

To link to this convention from code, the following header is recommended:

/** * @NOTE: The variable naming scheme used in this code is an adaption of * Systems Hungarian which is explained at http://blog.pother.ca/VariableNamingConvention/ */

The convention used for variables is a derived form of SystemsHungarian notation that consist of a 3 part prefix: the Scope of avariable, a Delimiter, and the Type of a variable.

For variables in a closed scope (usually a function) the Scope andDelimiter are omitted and only the Type is prefixed.

A delimiter is added in order to separate the scope from the rest of thename. This delimiter is a conscious eyesore to make variables from otherscopes stand out, as using variables from another scope can lead topainful situations.

Some languages require a variable name to start with asigil. Fordevelopers used to such a language, Hungarian Notation will feel morenatural than for developers used to languages that do not require sigils.

The letters used to denote the Scope and Type are explained in the"Scope" and "Type" sections below.

For the various languages this convention pertains to this gives us:

To help identify where variables come from and for easier fetching ofname-lists in scope-aware editors, a scope flag is prefixed to variablesthat aren't in a function/method's closed scope.

Available flags for the scope are:

• Moreinformation about types in PHP is available in the PHP manual
• More information about types in Javascript is available inthe MDN page on JavaScript data types and data structures
• More information about types in Bash is available in the Linux Documentation Project on theBash Guide page about Types of variables

1. In the Angular framework the dollar character$ has other significant, denoting a variable, parameter, property, or method that belongs to the core of Angular and prevent elements from being iterated (or interpreted) in certain directives.
2. The fact that this character can lead to confusion as it is a sigil in other languages has lead to the idea that it might be better to usej for jQuery objects instead. That idea is still under revision.
3. In Bash this refers to variables declared with the-f flag.
4. Javascript only has one "Number" type which is used for both floating-point numbers and integers
5. A string that has a value that represents an integer or double.

• Javascript (since ES6) has a "Symbol" type (also know as "Atoms" in other languages, similar to enumeration types).In PHP the closest thing to this is using aConstant.The Bash equivalent is declaring a variable readonly with the-r flag.As Symbols/Constants are the familiar exceptional to the rule and donot adhere to this standard. they should be declared in so called SCREAMING_SNAKE_CASE⁶

The "Name" part of a variable should describe what the variable is inthe problem domain it represents. Be as descriptive as possible buthold these two rules of thumb in the back of your head when coming upwith a name:

• Variable names should suggest a property or noun. UserName, Width, etc.
• Names should be descriptive, but also concise. Wherever possible, keepvariable names to under 3 words or 15 characters but be prepared tosacrifice a few extra characters to improve clarity.

Putting all of this together we get the following syntax diagram:

VariableName ::=  ( [$@%&]* ([gmpt] '_')*  [abcdfijmnorsu$] [A-Z] [a-zA-Z0-9]+ )

^{Generated using theRailroad Diagram Generator}

This convention has been evolving ever sincePotherca startedprogramming Perl in the mid-nineties and branched out into PHP in theearly noughties. Yet it was never put into writing until encourage to doso bySander Krause in 2009.

The Variable Naming Convention byPotherca and Sander Krause is licensed under the Creative Commons Attribution 4.0 International License .