The array_map() function in PHP is used to apply a callback function to each element of one or more arrays, returning a new array containing the results.

Syntax:

array_map(callback, array1, array2, ...)

• callback: A function (can be user-defined or built-in) to apply to the array elements.
• array1, array2, ...: One or more arrays. If more than one array is provided, the callback should accept that many parameters.

Example 1: Square each number in an array

$numbers = [1, 2, 3, 4, 5];

$squared = array_map(function($num) {
    return $num * $num;
}, $numbers);

print_r($squared);

Output:

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

Example 2: Using a built-in function — converting strings to uppercase

$names = ["alice", "bob", "charlie"];

$upperNames = array_map("strtoupper", $names);

print_r($upperNames);

Output:

Array
(
    [0] => ALICE
    [1] => BOB
    [2] => CHARLIE
)

Example 3: Multiple arrays – combining first and last names

$firstNames = ["John", "Jane", "Jim"];
$lastNames = ["Doe", "Smith", "Beam"];

$fullNames = array_map(function($first, $last) {
    return "$first $last";
}, $firstNames, $lastNames);

print_r($fullNames);

Output:

Array
(
    [0] => John Doe
    [1] => Jane Smith
    [2] => Jim Beam
)

Example 4: Return null callback (identity function)

If you pass null as the callback, array_map() will return the input array(s) as-is (used often when combining arrays):

$a = [1, 2, 3];
$b = ["a", "b", "c"];

$combined = array_map(null, $a, $b);

print_r($combined);

Output:

Array
(
    [0] => Array
        (
            [0] => 1
            [1] => a
        )

    [1] => Array
        (
            [0] => 2
            [1] => b
        )

    [2] => Array
        (
            [0] => 3
            [1] => c
        )
)