Using PHP’s array_map() Function: Basic and Advanced Usage

The array_map() function in PHP is a powerful utility that applies a callback to each element of one or more arrays and returns a new array with the transformed values.

1. Basic Usage of array_map()

The basic syntax of array_map() is:

<code>array_map(callable $callback, array ...$arr)</code>

The $callback parameter is the function or method that will be called for each element, and $arr represents the array(s) to be processed.

Example:

<code>$arr = [1, 2, 3];
$newArr = array_map(function($v) {
    return $v * 2;
}, $arr);
print_r($newArr);
</code>

Running this code outputs Array ( [0] => 2 [1] => 4 [2] => 6 ) , a new array where each original element has been multiplied by 2.

2. Advanced Usage of array_map()

Beyond the basic case, array_map() can handle multiple arrays and pass additional parameters to the callback.

Processing multiple arrays:

<code>$arr1 = [1, 2, 3];
$arr2 = [4, 5, 6];
$newArr = array_map(function($v1, $v2) {
    return $v1 + $v2;
}, $arr1, $arr2);
print_r($newArr);
</code>

This produces Array ( [0] => 5 [1] => 7 [2] => 9 ) , the element‑wise sum of the two arrays.

You can also pass extra arguments after the array parameters. Example:

<code>$arr = [1, 2, 3];
$prefix = 'num:';
$newArr = array_map(function($v, $prefix) {
    return $prefix . $v;
}, $arr, array_fill(0, count($arr), $prefix));
print_r($newArr);
</code>

The result is Array ( [0] => num:1 [1] => num:2 [2] => num:3 ) , where each element is prefixed with "num:".

Conclusion

The array_map() function is a convenient way to manipulate arrays in PHP; by providing different callbacks and parameters, you can perform a wide range of transformations. Pay attention to the number of arguments your callback expects to obtain the desired results.