The special NULL
value represents a variable with no value. NULL
is the
only possible value of type NULL.
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().
There is only one value of type null, and that is the
case-insensitive constant NULL
.
<?php
$var = NULL;
?>
Casting a variable to null using (unset) $var
will not remove the variable or unset its value.
It will only return a NULL
value.