(PHP 4 CVS only)
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);
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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
// )
//
// )
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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. Array_map() - 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
// )
//
// )
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See also array_filter(),
array_reduce().