Resources
Pseudo-types and variables used in this documentation
Types
PHP Manual

## NULL

The special `NULL` value represents a variable with no value. `NULL` is the only possible value of type NULL .

> Note: The null type was introduced in PHP 4.

A variable is considered to be null if:

- it has been assigned the constant `NULL`.

- it has not been set to any value yet.

- it has been unset().

### Syntax

There is only one value of type null , and that is the case-insensitive keyword `NULL`.

`<?php
$var = NULL;
?>`

See also the functions is_null() and unset().

### Casting to NULL

Casting a variable to null will remove the variable and unset its value.

Resources
Pseudo-types and variables used in this documentation
Types
PHP Manual