Description
array
array_map ( callback
function, 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()
範例 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 $b have:
Array
(
[0] = 1
[1] = 8
[2] = 27
[3] = 64
[4] = 125
)
|
|
範例 2. array_map() -
using more arrays
?php
function show_Spanish($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
範例 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().