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 ( callback 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);
?> |
上例将输出：
// 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);
?> |
上例将输出：
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()，array_walk() 和有关 callback 类型的信息。
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