variables.md

Variables

Use snake_case for variable naming.

When using snake_case, the difference between variables and functions is made more obvious, as functions use camelCase. Ambiguity is removed in abbreviations. For example, host_ip_address is obvious, whereas the difference between hostIpAddress and hostIPAddress is not.

Other identifiers within PHP use snake_case variations, such as constants' upper snake case (THIS_IS_A_CONSTANT). Using lower snake case for variables promotes consistentancy.

Snake case most closely resembles written words which helps readability in many occurences, especially when using variable names with Is and Ls closely together.

Never use global variables. Use a class to handle superglobals.

PHP supports object oriented programming, but global variables undermine some benefits introduced by OOP. Superglobals, such as $_GET, $_COOKIE, etc. should be handled by middleware before accessing.

Source code is most readable when scope is limited. Globals can be read and modified anywhere in any class, which makes it very difficult to track down usage.

There are many other cons for using globals, but in short, always think really hard when you're about to use a global variable.

Properties should always be declared.

PHP allows any property to be set on an object, from anywhere in the code. Some say this is a feature; some consider it bad practice. To aid readability and maintainability, always ensure that a class has the property declared before it is accessed or assigned.

Variables should always be declared at the top of the block they are used in.

To aid readability and maintainability, wherever a variable is used it should be assigned at the top of the block it is available to.

Languages like Java and C have their variables block scoped. Block scoping means that variables declared in a block between braces, including within if and for blocks, cannot be accessed from outside of that block.

In PHP however, variables are function scoped, meaning that all variables within a function are available to that function. It becomes difficult to read code where a variable is declared for the first time within a nested block of code, to then be later used in a parent block. To avoid unreadability, always declare variables at the top of the most-outer block they are used.