In PHP, a variable is a "container" for storing information. It is the name of the memory location that holds data. A variable starts with the $ sign, followed by the name of the variable. Unlike other programming languages, PHP has no command for declaring a variable. It is created the moment you first assign a value to it. The value of a variable is the value of its most recent assignment. Variables can be assigned with the = operator, with the variable on the left-hand side and the expression to be evaluated on the right. Here are some important things to know about variables in PHP:
- A variable does not need to be declared before adding a value to it. PHP automatically converts the variable to the correct data type, depending on its value.
- After declaring a variable, it can be reused throughout the code.
- A variable can have a short name (like x and y) or a more descriptive name (age, carname, total_volume) .
- 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 alphanumeric characters and underscores (A-z, 0-9, and _) .
- Variable names are case-sensitive.
In PHP, there is also a concept of "variable variables," which takes the value of a variable and treats that as the name of a variable.
