A variable can have a short name (like x and y) or a more descriptive name (age, carname, total_volume).
Rules for PHP variables
- 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 _ )
- Variable names are case-sensitive ($age and $AGE are two different variables)
PHP has three different variable scopes