php data type NULL

The special NULL value indicates that a variable has no value. The only possible value of type NULL is NULL.

A variable is considered NULL if:

is assigned a value of NULL.

has not been assigned a value yet.

is unset().

Syntax

The NULL type has only one value, which is the case-insensitive constant NULL.

<?php
$var = NULL;
?>

See is_null() and unset().

Convert to NULL

Using (unset) $var Converting a variable to null will not delete the variable or unset its value. Just returns NULL value.