php - array_map

Description

array array_map ( callback $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()

Parameters

callback

Callback function to run for each element in each array.

arr1

An array to run through the callback function.

array

Variable list of array arguments to run through the callback function.

Return Values

Returns an array containing all the elements of arr1 after applying the callback function to each one.

Examples

Example 252. array_map() example

<?phpfunction 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
)

Examples

Example 253. 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);
$d = array_map("map_Spanish", $a , $b);print_r($d);
The above example will output:

// 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

Example 254. 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);
The above example 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
        )

)