The **`is_null` method** can be used to check if a variable is `NULL` or not. 


#      
## Syntax

```
is_null(mixed $value): bool
```

The `is_null` method returns `true` if the passed value is `NULL`. Otherwise, it returns `false`.
 
## Code

<?php 

  printIsNull($test); // undefined variable is NULL

  $test = NULL;
  printIsNull($test);

  $test = 0;
  printIsNull($test);

  $test = 'NULL';
  printIsNull($test);

  function printIsNull($test){
    echo "The Value is: ";
    var_dump($test);

    echo "Is null: ";
    var_dump(is_null($test));
    
    echo "---------\n\n";
  }

?>

#      
## Explanation

In the code above:

* We use the `is_null` method to check if a variable is `NULL` or not.

* For the undeclared variable and for the value `NULL`, the `is_null` method returns `true`. 

* But for the values `0(int)` and `'NULL'(string)`, the `is_null` method returns `false` because they are not `NULL` values.

What Is the is_null method in PHP?

The is_null method checks if a variable is NULL, returning true if it is, false otherwise.