array_map

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 ( callable $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。

参数

 

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.

返回值

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

范例

 

Example #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
)

 

Example #2 array_map() using a lambda function (as of PHP 5.3.0)

<?php
$func  = function( $value ) {
    return  $value  *  2 ;
};

print_r ( array_map ( $func ,  range ( 1 ,  5 )));
?>

Array
(
    [0] => 2
    [1] => 4
    [2] => 6
    [3] => 8
    [4] => 10
)

 

Example #3 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 );
?>

以上例程会输出：

// 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。

 

Example #4 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 );
?>

以上例程会输出：

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
        ))

If the array argument contains string keys then the returned array will contain string keys if and only if exactly one array is passed. If more than one argument is passed then the returned array always has integer keys.

 

Example #5 array_map() - with string keys

<?php
$arr  = array( "stringkey"  =>  "value" );
function  cb1 ( $a ) {
    return array ( $a );
}
function  cb2 ( $a ,  $b ) {
    return array ( $a ,  $b );
}
var_dump ( array_map ( "cb1" ,  $arr ));
var_dump ( array_map ( "cb2" ,  $arr ,  $arr ));
var_dump ( array_map ( null ,   $arr ));
var_dump ( array_map ( null ,  $arr ,  $arr ));
?>

以上例程会输出：

array(1) {
  ["stringkey"]=>
  array(1) {
    [0]=>
    string(5) "value"
  }
}
array(1) {
  [0]=>
  array(2) {
    [0]=>
    string(5) "value"
    [1]=>
    string(5) "value"
  }
}
array(1) {
  ["stringkey"]=>
  string(5) "value"
}
array(1) {
  [0]=>
  array(2) {
    [0]=>
    string(5) "value"
    [1]=>
    string(5) "value"
  }
}

参见

 

• array_filter() - 用回调函数过滤数组中的单元
• array_reduce() - 用回调函数迭代地将数组简化为单一的值
• array_walk() - 对数组中的每个成员应用用户函数
• create_function() - Create an anonymous (lambda-style) function
• callback 类型的信息