How to Use array_map in PHP: Syntax and Examples

In PHP, array_map applies a callback function to each element of one or more arrays and returns a new array with the results. You pass the callback as the first argument and the array(s) to transform as the following arguments.

Syntax

The array_map function takes a callback function and one or more arrays. It applies the callback to each element of the arrays and returns a new array with the transformed values.

• callback: A function to apply to each element.
• array1, array2, ...: One or more arrays to process.

php

array array_map ( callable $callback , array $array1 [, array ...$arrays ] )

Example

This example shows how to use array_map to square each number in an array.

php

<?php
$numbers = [1, 2, 3, 4, 5];
$squares = array_map(fn($n) => $n * $n, $numbers);
print_r($squares);
?>

Output

Array
(
    [0] => 1
    [1] => 4
    [2] => 9
    [3] => 16
    [4] => 25
)

Common Pitfalls

Common mistakes include:

• Passing a non-callable as the first argument, which causes an error.
• Using array_map with multiple arrays of different lengths, which processes only up to the shortest array length.
• Not returning a value from the callback, resulting in null elements.

php

<?php
// Wrong: callback missing
// $result = array_map('not_a_function', [1, 2, 3]); // Fatal error

// Right: callback returns value
$result = array_map(fn($x) => $x + 1, [1, 2, 3]);
print_r($result);

// Multiple arrays of different lengths
$a = [1, 2, 3];
$b = [4, 5];
$sum = array_map(fn($x, $y) => $x + $y, $a, $b);
print_r($sum);
?>

Output

Array
(
    [0] => 2
    [1] => 3
    [2] => 4
)
Array
(
    [0] => 5
    [1] => 7
)

Quick Reference

Parameter	Description
callback	Function applied to each element
array1	First array to process
array2, ...	Optional additional arrays to process in parallel
Return	New array with callback results

Key Takeaways

Use array_map to apply a function to each element of one or more arrays and get a new array.

The callback must return a value; otherwise, the result will contain nulls.

When using multiple arrays, array_map stops at the shortest array length.

Always pass a valid callable as the first argument to avoid errors.

array_map is useful for transforming arrays without writing loops.