PHP | is_null() Function

The is_null() function is an inbuilt function in PHP which is used to find whether a variable is NULL or not.

Syntax:

 boolean is_null ( $var )

Parameters: This function accepts a single parameter as shown in above syntax and described below.  

• $var: Variable to check if it is NULL or not.

Return value: It returns a boolean value. That is, it returns TRUE when $var will be NULL, otherwise it returns FALSE.

Below programs illustrate the is_null() function in PHP:

Program 1:

PHP

<?php
// PHP code to demonstrate the working of is_null() function
$var1 = NULL;
$var2 = "\0"; // "\0" means "\0"
$var3 = "NULL";
$var4 = 0;

// $var1 has NULL value, so always give TRUE
is_null($var1) ? print_r("True\n") : print_r("False\n");

// $var2 has '\0' value which consider as null in
// c and c++ but here taken as string, gives FALSE
is_null($var2) ? print_r("True\n") : print_r("False\n");

// $var3 has NULL string value so it will false
is_null($var3) ? print_r("True\n") : print_r("False\n");

// $var4 is 0, gives FALSE
is_null($var4) ? print_r("True\n") : print_r("False\n");

?>

Output: 

True
False
False
False

Program 2:

PHP

<?php
// PHP code to demonstrate the working of
// is_null() function

function check_null($var)
{
    return (is_null($var) ? "True" : "False");
}

echo check_null(NULL) . "\n";
echo check_null(null) . "\n";
echo check_null(Null) . "\n";
echo check_null(NUll) . "\n";
echo check_null(NULl) . "\n";
echo check_null(nulL) . "\n";
echo check_null(nuLL) . "\n";
echo check_null(nULL) . "\n";

echo check_null(Nul) . "\n";
echo check_null(false) . "\n";

?>

Output: 

True
True
True
True
True
True
True
True
False
False

Reference: http://php.net/manual/en/function.is-null.php