Closures and variable binding with use in PHP - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a closure that uses the variable $x.

PHP

<?php
$x = 5;
$func = function() use ([1]) {
    return $x * 2;
};
echo $func();
?>

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

A$x

B$y

C$z

D$a

Attempts:

3 left

💡 Hint

Common Mistakes

Using a variable name not defined outside the closure.

Forgetting to use the use keyword.

The use keyword imports the variable $x into the closure's scope.

2fill in blank

medium

Complete the code to modify the external variable $count inside the closure.

PHP

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

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

A$value

B$count

C$num

D$total

Attempts:

3 left

💡 Hint

Common Mistakes

Not using & to pass by reference.

Using a different variable name inside use.

Using &$count imports the variable by reference, allowing the closure to modify it.

3fill in blank

hard

Fix the error in the closure by correctly importing the variable $name.

PHP

<?php
$name = "Alice";
$greet = function() use ([1]) {
    return "Hello, " . $name;
};
echo $greet();
?>

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

A$this->name

B$_name

C$name

D$greet

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to access external variables directly inside the closure.

Using incorrect variable names.

The closure must import $name using use ($name) to access it inside.

4fill in blank

hard

Fill both blanks to create a closure that captures $a and $b by value and returns their sum.

PHP

<?php
$a = 3;
$b = 4;
$sum = function() use ([1], [2]) {
    return [1] + [2];
};
echo $sum();
?>

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

A$a

B$b

C$c

D$d

Attempts:

3 left

💡 Hint

Common Mistakes

Using variables not defined outside the closure.

Not importing variables with use.

The closure imports $a and $b by value and returns their sum.

5fill in blank

hard

Fill all three blanks to create a closure that captures $x by reference, increments it, and returns the new value.

PHP

<?php
$x = 10;
$increment = function() use ([1]) {
    [2]++;
    return [3];
};
echo $increment();
?>

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

A&$x

B$x

D$y

Attempts:

3 left

💡 Hint

Common Mistakes

Not using reference in use.

Using different variable names inside the closure.

The closure imports $x by reference using &$x, increments it, and returns the updated value.