(PHP 4 >= 4.0.6)
array_map -- Applies the callback to the elements of the given arrays
Description
array array_map (mixed callback, 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()
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Example 1. array_map() example
function cube($n) {
return $n*$n*$n;
}
$a = array(1, 2, 3, 4, 5);
$b = array_map("cube", $a);
print_r($b);
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This makes $b have:
Array
(
[0] => 1
[1] => 8
[2] => 27
[3] => 64
[4] => 125
)
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Example 2. array_map() - using more arrays
function show_Spanish($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);
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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
)
)
|
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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
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Example 3. Creating an array of arrays
$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);
|
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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
)
)
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See also array_filter() and array_reduce().
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