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# array_map

(PHP 4 >= 4.0.6)

array_map -- Applies the callback to the elements of the given arrays

## Description

``array array_map` (mixed callback, array arr1 [, array arr2...])`

array_map() returns an array containing all the elements of `arr1` after applying the callback function to each one. The number of parameters that the callback function accepts should match the number of arrays passed to the array_map()

Example 1. array_map() example
    function cube($n) {
        return $n*$n*$n;
    }

    $a = array(1, 2, 3, 4, 5);
    $b = array_map("cube", $a);

This will result in `$b` containing `array (1, 8, 27, 64, 125);`

Example 2. array_map() - using more arrays
    function show_Spanish($n, $m) {
        return "The number $n is called $m in Spanish";
    }

    function map_Spanish($n, $m) {
        return array ($n => $m);
    }

    $a = array(1, 2, 3, 4, 5);
    $b = array("uno", "dos", "tres", "cuatro", "cinco");

    $c = array_map("show_Spanish", $a, $b);

    print_r($c);

    // will output:
    // Array
    // (
    //     [0] => The number 1 is called uno in Spanish
    //     [1] => The number 2 is called dos in Spanish
    //     [2] => The number 3 is called tres in Spanish
    //     [3] => The number 4 is called cuatro in Spanish
    //     [4] => The number 5 is called cinco in Spanish
    // )

    $d = array_map("map_Spanish", $a , $b);

    print_r($d);

    // will output:
    // Array
    // (
    //     [0] => Array
    //         (
    //             [1] => uno
    //         )
    //
    //     [1] => Array
    //         (
    //             [2] => dos
    //         )
    //
    //     [2] => Array
    //         (
    //             [3] => tres
    //         )
    //
    //     [3] => Array
    //         (
    //             [4] => cuatro
    //         )
    //
    //     [4] => Array
    //         (
    //             [5] => cinco
    //         )
    //
    // )

Usually when using two or more arrays, they should be of equal length because the callback function is applied in parallel to the corresponding elements. If the arrays are of unequal length, the shortest one will be extended with empty elements.

An interesting use of this function is to construct an array of arrays, which can be easily performed by using `NULL` as the name of the callback function

Example 3. Creating an array of arrays
    $a = array(1, 2, 3, 4, 5);
    $b = array("one", "two", "three", "four", "five");
    $c = array("uno", "dos", "tres", "cuatro", "cinco");

    $d = array_map(null, $a, $b, $c);
    print_r($d);

    // will output:
    // Array
    // (
    //     [0] => Array
    //         (
    //             [0] => 1
    //             [1] => one
    //             [2] => uno
    //         )
    //
    //     [1] => Array
    //         (
    //             [0] => 2
    //             [1] => two
    //             [2] => dos
    //         )
    //
    //     [2] => Array
    //         (
    //             [0] => 3
    //             [1] => three
    //             [2] => tres
    //         )
    //
    //     [3] => Array
    //         (
    //             [0] => 4
    //             [1] => four
    //             [2] => cuatro
    //         )
    //
    //     [4] => Array
    //         (
    //             [0] => 5
    //             [1] => five
    //             [2] => cinco
    //         )
    //
    // )

See also array_filter(), array_reduce().

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