Using PHP's array_map() Function: Syntax, Examples, and Summary

PHP is a widely used scripting language for web development that provides many built-in functions. The array_map() function is a powerful utility that applies a callback to each element of one or more arrays and returns a new array with the processed values.

array_map() Function Syntax

<code>array_map(callback, array1, array2...)</code>

The callback is the function to be executed, and array1 , array2 , etc., are the arrays to be processed. array_map() applies the callback to each element of the provided arrays in order and returns a new array containing the results.

Below is a simple example that squares each number in an array of five integers:

<code>// Define the callback function
function square($num) {
    return $num * $num;
}

// Define the array to process
$numbers = [1, 2, 3, 4, 5];

// Apply array_map() with the callback
$result = array_map('square', $numbers);

// Output the result
print_r($result);
</code>

The output is:

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

In this example, we first define a named callback function square() that returns the square of its argument. We then create an array $numbers containing five numbers and call array_map() to apply square() to each element, storing the transformed values in $result . Finally, print_r() displays the new array.

Besides named callbacks, anonymous functions can also be used. The following example converts each string in an array to uppercase using an anonymous function:

<code>// Define the array to process
$strings = ["hello", "world", "php", "array", "map"];

// Use an anonymous function as the callback
$result = array_map(function($string) {
    return strtoupper($string);
}, $strings);

// Output the result
print_r($result);
</code>

The output is:

<code>Array
(
    [0] => HELLO
    [1] => WORLD
    [2] => PHP
    [3] => ARRAY
    [4] => MAP
)
</code>

Here, an anonymous function receives each string, converts it to uppercase with strtoupper() , and returns the result. array_map() processes each element of $strings , stores the transformed values in $result , and print_r() displays the final array.

Summary

The array_map() function is a very useful array-processing tool in PHP. It can apply any callable—named or anonymous—to each element of one or more arrays, returning a new array with the processed values. The examples above demonstrate basic usage and show how array_map() simplifies array transformations, making development more efficient.