Nullable types in functions in PHP - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a nullable integer parameter in the function.

PHP

<?php
function example([1] $num) {
    return $num;
}
?>

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

Astring

B?int

Cfloat

Dint

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting the question mark and just using 'int' which disallows null.

Using a wrong type like 'string' when integer is needed.

The ?int syntax declares that the parameter can be an integer or null.

2fill in blank

medium

Complete the function return type to allow returning an integer or null.

PHP

<?php
function getValue(): [1] {
    return null;
}
?>

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

A?int

Bvoid

Cint

Dstring

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'int' alone disallows returning null.

Using 'void' which means no return value.

The return type ?int means the function can return an integer or null.

3fill in blank

hard

Fix the error in the function parameter type to accept null or string.

PHP

<?php
function greet([1] $name) {
    if ($name === null) {
        return 'Hello, Guest!';
    }
    return "Hello, $name!";
}
?>

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

A?string

Bstring

Cint

Dbool

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'string' alone which disallows null.

Using unrelated types like 'int' or 'bool'.

Using ?string allows the parameter to be a string or null.

4fill in blank

hard

Fill both blanks to declare a function with a nullable float parameter and nullable float return type.

PHP

<?php
function calculate([1] $value): [2] {
    if ($value === null) {
        return null;
    }
    return $value * 2;
}
?>

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

A?float

Bfloat

Dint

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'float' without question mark disallows null.

Mixing types like 'int' and 'float'.

Both the parameter and return type use ?float to allow float or null.

5fill in blank

hard

Fill all three blanks to create a function with a nullable string parameter, nullable int parameter, and nullable string return type.

PHP

<?php
function process([1] $text, [2] $count): [3] {
    if ($text === null || $count === null) {
        return null;
    }
    return str_repeat($text, $count);
}
?>

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

A?string

B?int

Dint

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting question marks, disallowing null.

Using wrong types like 'int' for string parameters.

The parameters and return type use nullable types: ?string and ?int.