- A variable starts with the

$

sign, followed by the name of the variable - A variable name must start with a letter or the underscore character - A variable name cannot start with a

number

- A variable name can only contain alpha-numeric characters and underscores (

A-z

,

0-9

, and

_

)

// Correct Syntax
$variable_name = "Value";

// Incorrect Syntax
Variable_Name = "Value";
$5variable_name = "Value";
$variable-name = "Value";