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# array_map

(PHP 4 >= 4.0.6, PHP 5)

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

## Description

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

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()

예 1. array_map() example

`<?php function cube($n) { return($n * $n * $n); } $a = array(1, 2, 3, 4, 5); $b = array_map("cube", $a); print_r($b); ?>`

This makes `$b` have:

    Array
    (
        [0] => 1
        [1] => 8
        [2] => 27
        [3] => 64
        [4] => 125
    )

예 2. array_map() - using more arrays

`<?php 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); $d = array_map("map_Spanish", $a , $b); print_r($d); ?>`

This results:

    // printout of $c
    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
    )

    // printout of $d
    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

예 3. Creating an array of arrays

`<?php $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); ?>`

The printout of the program above will be:

    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(), and array_walk().

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