Why closures matter in PHP - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a closure that returns a greeting.

PHP

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

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

Aname

Bname()

C$this

D$name

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting the $ sign before the variable name.

Using a variable name not defined in the function parameters.

The closure uses the parameter $name to build the greeting string.

2fill in blank

medium

Complete the code to use the 'use' keyword to access an external variable inside a closure.

PHP

<?php
$message = 'Hello';
$greet = [1]($name) use ($message) {
    return $message . ', ' . $name . '!';
};
echo $greet('Bob');
?>

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

Afn

Bclosure

Cfunction

Dcallable

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'fn' instead of 'function' when 'use' is needed.

Not including the 'use' keyword to access external variables.

The closure is defined with the function keyword and uses use to access $message from outside.

3fill in blank

hard

Fix the error in the closure to correctly modify the external variable by reference.

PHP

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

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

Acount

Bincrement

Ccounter

Dvalue

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different variable name inside the closure.

Not passing the variable by reference with &.

The variable $count is passed by reference using &$count so the closure can modify it.

4fill in blank

hard

Fill both blanks to create a closure that filters an array using an external threshold variable.

PHP

<?php
$threshold = 10;
$numbers = [5, 12, 8, 20];
$filtered = array_filter($numbers, function($num) use ([1]) {
    return $num [2] $threshold;
});
print_r($filtered);
?>

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

A$threshold

B>

C<

D$num

Attempts:

3 left

💡 Hint

Common Mistakes

Not using the 'use' keyword to access the external variable.

Using the wrong comparison operator.

The closure uses use ($threshold) to access the external variable and filters numbers greater than the threshold.

5fill in blank

hard

Fill all three blanks to create a closure that returns a multiplier function with a captured factor.

PHP

<?php
function multiplier($factor) {
    return function($number) use ([1]) {
        return $number [2] [3];
    };
}
$double = multiplier(2);
echo $double(5);
?>

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

A$factor

B*

D+

Attempts:

3 left

💡 Hint

Common Mistakes

Not capturing the variable with 'use'.

Using the wrong operator for multiplication.

The closure captures $factor and multiplies the input number by it.