is_null in PHP

is_null — Finds whether a variable is NULL


Syntax: 
bool is_null ( mixed $var )

Finds whether the given variable is NULL.
Parameters: 

var

    The variable being evaluated.

Return Values:

Returns TRUE if var is null, FALSE otherwise.
Examples:

Example #1 is_null() example
<?php

error_reporting(E_ALL);

$foo = NULL;
var_dump(is_null($inexistent), is_null($foo));

?>

Notice: Undefined variable: inexistent in ...
bool(true)
bool(true)