freeCodeCamp/guide/english/php/PHP Variables/index.md

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PHP Variables

PHP - Vaiables Types

Varibles are the main way to store information in the middle way of a PHP program. All variables in PHP are donated with a leading dollar sign like $variable_name. Variables are assigned with the = operator , with the variable on the left-hand side and the expression to be evaluated on the right.

Variable Naming

Rules for naming a variable is listed below:

1. Variables names must begin with a letter or underscores character.
2. A variable name can consist of numbers, letters, underscores but you cannot use characters like + , - , % , ( , ) . & in its name.
3. Variable names are case-sensitive i.e. ($age and $AGE are two different variables).

Creating (Declaring) PHP Variables

In PHP, a variable starts with the $ sign, followed by the name of the variable. The code snippet given below shows it.

 <?php
    $txt = "Hello world!";
    $x = 6;
    $y = 10.5;
 ?>

Variable lifecycle: In PHP variables have a default value. If a variable is not declared before you attempt to use it, its value will be NULL. It is unset. So you can't use it by writing isset($variable) before using it.