PHP array_map Function

last modified March 13, 2025

The PHP array_map function applies a callback to each element of one or more arrays. It returns a new array with transformed elements.

Basic Definition

The array_map function processes each array element through a callback function. It creates a new array with the returned values.

Syntax: array_map(callable $callback, array $array, array ...$arrays): array. The callback receives array elements as arguments and returns transformed values.

Basic array_map Example

This example demonstrates squaring each number in an array using array_map.

basic_array_map.php

<?php

declare(strict_types=1);

$numbers = [1, 2, 3, 4, 5];
$squared = array_map(fn($n): int => $n * $n, $numbers);

print_r($squared);
// Output: Array ( [0] => 1 [1] => 4 [2] => 9 [3] => 16 [4] => 25 )

The callback squares each number. array_map returns a new array with the squared values while preserving the original array's structure.

Processing Multiple Arrays

array_map can process multiple arrays simultaneously.

multiple_arrays.php

<?php

declare(strict_types=1);

$names = ["Alice", "Bob", "Charlie"];
$ages = [25, 30, 35];

$combined = array_map(
    fn($name, $age): string => "$name is $age years old",
    $names,
    $ages
);

print_r($combined);
// Output: Array ( [0] => Alice is 25 years old [1] => Bob is 30 years old... )

This combines corresponding elements from two arrays into strings. The callback receives one element from each array in the same position.

Using Named Functions

You can use named functions instead of anonymous functions for complex logic.

named_function.php

<?php

declare(strict_types=1);

function formatPrice(float $price): string {
    return '$' . number_format($price, 2);
}

$prices = [19.99, 29.95, 9.50];
$formatted = array_map('formatPrice', $prices);

print_r($formatted);
// Output: Array ( [0] => $19.99 [1] => $29.95 [2] => $9.50 )

The formatPrice function formats each price with a dollar sign and two decimal places. The function name is passed as a string to array_map.

Working with Array Keys

array_map doesn't preserve keys by default, but we can work around this.

preserving_keys.php

<?php

declare(strict_types=1);

$data = ['a' => 1, 'b' => 2, 'c' => 3];
$result = array_map(
    fn($value, $key): array => [$key => $value * 2],
    $data,
    array_keys($data)
);

$final = array_merge(...$result);
print_r($final);
// Output: Array ( [a] => 2 [b] => 4 [c] => 6 )

This example shows how to preserve keys by passing array_keys as a second array. The result is then merged to recreate the original associative array structure.

Advanced: Using array_map with Objects

array_map can transform object properties or call methods.

object_transformation.php

<?php

declare(strict_types=1);

class User {
    public function __construct(
        public string $name,
        public string $email
    ) {}
    
    public function getDomain(): string {
        return explode('@', $this->email)[1];
    }
}

$users = [
    new User('Alice', 'alice@example.com'),
    new User('Bob', 'bob@domain.com'),
    new User('Charlie', 'charlie@test.com')
];

$domains = array_map(fn(User $u): string => $u->getDomain(), $users);

print_r($domains);

This extracts email domains from User objects. The callback calls the getDomain method on each object, demonstrating object-oriented use of array_map.

Best Practices

Type Safety: Use type hints in callbacks for better code reliability.
Readability: Prefer named functions for complex transformations.
Performance: Avoid expensive operations in large array processing.
Immutability: Remember array_map creates new arrays without modifying originals.

Source

PHP array_map Documentation

This tutorial covered the PHP array_map function with practical examples showing its usage for array transformation scenarios.

Author

My name is Jan Bodnar, and I am a passionate programmer with extensive programming experience. I have been writing programming articles since 2007. To date, I have authored over 1,400 articles and 8 e-books. I possess more than ten years of experience in teaching programming.

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