array_map
(PHP 4 >= 4.0.6, PHP 5)
array_map --
将回调函数作用到给定数组的单元上
说明
array
array_map ( mixed callback, array arr1 [, array ...] )
array_map() 返回一个数组,该数组包含了
arr1 中的所有单元经过
callback 作用过之后的单元。callback
接受的参数数目应该和传递给
array_map() 函数的数组数目一致。
例子 1. array_map() 例子
<?php function cube($n) { return $n*$n*$n; }
$a = array(1, 2, 3, 4, 5); $b = array_map("cube", $a); print_r($b); ?>
|
这使得 $b 成为:
Array
(
[0] => 1
[1] => 8
[2] => 27
[3] => 64
[4] => 125
) |
|
例子 2. array_map() - 使用更多的数组
<?php function show_Spanish($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); ?>
|
结果为:
// 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
)
) |
|
通常使用了两个或更多数组时,它们的长度应该相同,因为回调函数是平行作用于相应的单元上的。如果数组的长度不同,则最短的一个将被用空的单元扩充。
本函数一个有趣的用法是构造一个数组的数组,这可以很容易的通过用 NULL 作为回调函数名来实现。
例子 3. 建立一个数组的数组
<?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); ?>
|
|
以上程序输出为:
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
)
) |
参见 array_filter(),array_reduce()
和 array_walk()。