Closures as callbacks in PHP - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a closure that prints a message.

PHP

<?php
$message = function() { echo [1]; };
$message();
?>

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

A"Hello, world!"

BHello, world!

Cecho "Hello, world!"

Dprint("Hello, world!")

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to put quotes around the string.

Trying to echo inside the closure argument.

The closure must echo a string, so the string must be quoted.

2fill in blank

medium

Complete the code to pass a closure as a callback to array_map.

PHP

<?php
$numbers = [1, 2, 3];
$squares = array_map([1], $numbers);
print_r($squares);
?>

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

Afunction($n) { echo $n; }

Bfunction($n) { return $n * $n; }

Cfn($n) => $n + $n

Dfunction $n { return $n * $n; }

Attempts:

3 left

💡 Hint

Common Mistakes

Missing parentheses around the parameter.

Using echo instead of return.

The closure must be a function that returns the square of the number.

3fill in blank

hard

Fix the error in the closure that uses a variable from the parent scope.

PHP

<?php
$multiplier = 3;
$multiply = function($n) [1] {
    return $n * $multiplier;
};
echo $multiply(5);
?>

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

Aimport ($multiplier)

Bwith ($multiplier)

Cuse ($multiplier)

Dcapture ($multiplier)

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect keywords like 'with' or 'import'.

Not including the variable in the use clause.

In PHP, to use a variable from the parent scope inside a closure, you must use the use keyword.

4fill in blank

hard

Fill both blanks to create a closure that modifies a variable by reference.

PHP

<?php
$count = 0;
$increment = [1] use ([2]) {
    $count++;
};
$increment();
echo $count;
?>

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

Afunction()

B&$count

C$count

Dfunction(&$count)

Attempts:

3 left

💡 Hint

Common Mistakes

Not using the ampersand to pass by reference.

Trying to pass the variable as a parameter instead of use clause.

The closure is defined as a function with no parameters, but it uses $count by reference with &$count in the use clause.

5fill in blank

hard

Fill all three blanks to create a closure that filters an array using a condition.

PHP

<?php
$words = ['apple', 'bee', 'cat', 'dog'];
$minLength = 3;
$longWords = array_filter($words, function([1]) use ([2]) {
    return strlen([3]) > [2];
});
print_r($longWords);
?>

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

A$word

B$minLength

D$length

Attempts:

3 left

💡 Hint

Common Mistakes

Using inconsistent variable names.

Not passing the external variable with use.

The closure takes $word as parameter, uses $minLength from parent scope, and checks the length of $word.