Special type Null (empty type) in PHP

The special value NULL indicates that this variable does not matter. NULL is the only possible value of type NULL .

A variable is considered NULL if

• it was assigned the constant NULL .

• she has not yet been assigned any value.

• it was removed with unset () .

Special NULL syntax

There is only one NULL value , the case-insensitive keyword NULL .

$var = NULL;
?>

See also is_null () and unset () .