如何使用array_map来指定键？

Question

Using the canonical PHPdoc example, this code:

<?php
function cube($n)
{
    return($n * $n * $n);
}

$a = array( 3, 4, 5);
$b = array_map("cube", $a);
print_r($b);
?>

outputs

Array

(
    [0] => 27
    [1] => 64
    [2] => 125
)

But what I really want it to output is something along these lines: Array

(
    [3] => 27
    [4] => 64
    [5] => 125
)

That is, I want the array_map to use the same keys as in the original array. Is there any way to do that? Thanks!

Answer 1

Use array_combine():

$b = array_combine( $a, array_map("cube", $a));

You can see from this demo that it produces:

Array
(
    [3] => 27
    [4] => 64
    [5] => 125
)