Array map function in PHP - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the array_map function do in PHP?

It applies a callback function to each element of one or more arrays and returns a new array with the modified elements.

beginner

How do you pass a function to array_map?

You pass the function name as a string or an anonymous function as the first argument to array_map.

intermediate

What happens if you pass multiple arrays to array_map?

The callback function receives elements from each array as arguments, and array_map processes elements with the same keys together.

beginner

Example: What is the output of this code?<br>

$numbers = [1, 2, 3];
$result = array_map(fn($n) => $n * 2, $numbers);
print_r($result);

The output is:<br>

Array
(
    [0] => 2
    [1] => 4
    [2] => 6
)

<br>Each number is doubled by the callback function.

intermediate

Why is array_map useful compared to a foreach loop?

array_map is more concise and expressive for transforming arrays, making code easier to read and maintain.

What is the first argument of array_map in PHP?

A A callback function

B An array to modify

C A string to append

D A number to multiply

The first argument must be a callback function that defines how to transform each element.

What does array_map return?

A An integer count

B The original array unchanged

C A boolean value

D A new array with transformed elements

array_map returns a new array with each element modified by the callback.

If you pass two arrays to array_map, how many arguments does the callback receive?

A One argument

B Two arguments

C Zero arguments

D Three arguments

The callback receives one element from each array as separate arguments.

Which of these is a valid way to use array_map?

A array_map('strtoupper', ['a', 'b', 'c']);

B array_map(['a', 'b', 'c'], 'strtoupper');

C array_map('strtoupper');

D array_map();

The first argument is the callback function name, the second is the array.

What happens if the arrays passed to array_map have different lengths?

A An error is thrown

B The callback runs until the longest array ends

C The callback runs until the shortest array ends

D Only the first array is processed

Processing stops when the shortest array runs out of elements.

Explain how the array_map function works in PHP and give a simple example.

Think about how you change each item in a list using a function.

Describe what happens when you pass multiple arrays to array_map and how the callback function handles them.

Imagine pairing items from two lists and processing them together.