Arrow functions (short closures) in PHP - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create an arrow function that returns the square of a number.

PHP

$square = fn($x) => [1];
echo $square(4);

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

A$x + $x

B2 * $x

C$x - 2

D$x * $x

Attempts:

3 left

💡 Hint

Common Mistakes

Using addition instead of multiplication.

Forgetting to use the variable inside the function.

The arrow function returns the square by multiplying the input by itself.

2fill in blank

medium

Complete the code to create an arrow function that adds 10 to a number.

PHP

$addTen = fn($num) => [1];
echo $addTen(5);

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

A$num + 10

B$num * 10

C10 - $num

D$num - 10

Attempts:

3 left

💡 Hint

Common Mistakes

Subtracting instead of adding.

Multiplying instead of adding.

The arrow function adds 10 to the input number.

3fill in blank

hard

Fix the error in the arrow function that should return the length of a string.

PHP

$length = fn($str) => [1];
echo $length('hello');

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

Acount($str)

Blength($str)

Cstrlen($str)

Dsize($str)

Attempts:

3 left

💡 Hint

Common Mistakes

Using length() which is not a PHP function.

Using count() which is for arrays.

The correct PHP function to get string length is strlen().

4fill in blank

hard

Fill both blanks to create an arrow function that filters an array to keep only numbers greater than 5.

PHP

$filter = fn($arr) => array_filter($arr, fn($n) => $n [1] [2]);
print_r($filter([3, 7, 2, 9]));

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

A>

B5

C<

D7

Attempts:

3 left

💡 Hint

Common Mistakes

Using < instead of >.

Using wrong threshold number.

The arrow function uses > 5 to keep numbers greater than 5.

5fill in blank

hard

Fill all three blanks to create an arrow function that maps an array to its elements doubled if they are even.

PHP

$doubleEven = fn($arr) => array_map(fn($x) => [1] ? [2] : [3], $arr);
print_r($doubleEven([1, 2, 3, 4]));

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

A$x % 2 === 0

B$x * 2

C$x

D$x + 2

Attempts:

3 left

💡 Hint

Common Mistakes

Using addition instead of multiplication for doubling.

Not checking for even numbers correctly.

The arrow function checks if a number is even, doubles it if true, otherwise returns it unchanged.