Null type and its meaning in PHP - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to assign a null value to the variable.

PHP

<?php
$var = [1];
?>

Drag options to blanks, or click blank then click option'

Afalse

B0

C"null"

Dnull

Attempts:

3 left

💡 Hint

Common Mistakes

Using 0 or false instead of null.

Using the string "null" instead of the null value.

In PHP, null is the special value used to represent a variable with no value.

2fill in blank

medium

Complete the code to check if a variable is null.

PHP

<?php
if ([1]($var)) {
    echo "Variable is null.";
}
?>

Drag options to blanks, or click blank then click option'

Ais_null

Bisset

Cempty

Dis_string

Attempts:

3 left

💡 Hint

Common Mistakes

Using isset() which returns false if variable is null but also false if variable is not set.

Using empty() which returns true for many values, not just null.

The function is_null() returns true if the variable is null.

3fill in blank

hard

Fix the error in the code to correctly assign null to the variable.

PHP

<?php
$var = [1];
?>

Drag options to blanks, or click blank then click option'

ANULL

BNull

Cnull

D"null"

Attempts:

3 left

💡 Hint

Common Mistakes

Using uppercase NULL, which is accepted but lowercase is preferred.

Using quotes which makes it a string, not null.

In PHP, the null value is null (case-insensitive, but lowercase is standard and preferred). Using quotes makes it a string, not null.

4fill in blank

hard

Fill both blanks to create an array with keys and values where some values are null.

PHP

<?php
$data = [
    'name' => 'Alice',
    'age' => [1],
    'email' => [2]
];
?>

Drag options to blanks, or click blank then click option'

Anull

B"[e-mail]"

C0

Dfalse

Attempts:

3 left

💡 Hint

Common Mistakes

Using 0 or false instead of null for missing age.

Not using quotes around the email string.

The 'age' key has a null value, meaning no age is set. The 'email' key has a string value.

5fill in blank

hard

Fill all three blanks to create a function that returns null if input is empty, else returns input.

PHP

<?php
function checkInput($input) {
    if (empty($input)) {
        return [1];
    } else {
        return [2];
    }
}

$result = checkInput([3]);
?>

Drag options to blanks, or click blank then click option'

Anull

B$input

C""

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Returning 0 or false instead of null for empty input.

Not returning the input variable in the else branch.

Calling the function with a value other than an empty string.

The function returns null if the input is empty (like an empty string), otherwise it returns the input itself. The function is called with an empty string.