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array_map — Wendet eine Callback-Funktion auf die Elemente von Arrays an
array_map() gibt ein Array mit allen Elementen von arr1 zurück, nachdem die Callback-Funktion callback auf jedes einzelne Element angewandt wurde. Die Anzahl Parameter, welche die Callback-Funktion callback akzeptiert, sollte der Anzahl der an array_map() übergebenen Arrays entsprechen.
Callback-Funktion, die für jedes Element in jedem Array aufgerufen werden soll.
Ein Array, auf das die callback-Funktion angewendet werden soll.
Variable Liste von Array-Argumenten, auf die die callback-Funktion angewendet werden soll.
Gibt ein Array zurück, dass alle Elemente von arr1 enthält, nachdem die callback-Funktion auf jedes Element angewendet wurde.
Beispiel #1 array_map()-Beispiel
<?php
function cube($n)
{
return($n * $n * $n);
}
$a = array(1, 2, 3, 4, 5);
$b = array_map("cube", $a);
print_r($b);
?>
Dies speichert in $b:
Array
(
[0] => 1
[1] => 8
[2] => 27
[3] => 64
[4] => 125
)
Beispiel #2 array_map() mit einer Lambda-Funktion (seit PHP 5.3.0)
<?php
/* Seit PHP 5.3.0 */
$func = function($value) { return $value * 2; };
print_r(array_map($func, range(1, 5)));
?>
Array
(
[0] => 2
[1] => 4
[2] => 6
[3] => 8
[4] => 10
)
Beispiel #3 array_map() - Verwendung mehrerer Arrays
<?php
function show_Spanish($n, $m)
{
return("Die Zahl $n heißt auf Spanisch $m");
}
function map_Spanish($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);
?>
Das oben gezeigte Beispiel erzeugt folgende Ausgabe:
// Ausgabe von $c
Array
(
[0] => Die Zahl 1 heißt auf Spanisch uno
[1] => Die Zahl 2 heißt auf Spanisch dos
[2] => Die Zahl 3 heißt auf Spanisch tres
[3] => Die Zahl 4 heißt auf Spanisch cuatro
[4] => Die Zahl 5 heißt auf Spanisch cinco
)
// Ausgabe von $d
Array
(
[0] => Array
(
[1] => uno
)
[1] => Array
(
[2] => dos
)
[2] => Array
(
[3] => tres
)
[3] => Array
(
[4] => cuatro
)
[4] => Array
(
[5] => cinco
)
)
Bei Verwendung von zwei oder mehr Arrays sollten diese gewöhnlich die gleiche Länge besitzen, da die Callback-Funktion parallel auf die entsprechenden Elemente angewandt wird. Haben die Arrays unterschiedliche Längen, wird das kürzeste um leere Elemente erweitert.
Eine interessante Anwendung dieser Funktion ist die Konstruktion eines Arrays bestehend aus Arrays, was mit NULL als Name der Callback-Funktion leicht realisiert werden kann.
Beispiel #4 Erstellen eines Arrays mit Arrays
<?php
$a = array(1, 2, 3, 4, 5);
$b = array("eins", "zwei", "drei", "vier", "fünf");
$c = array("uno", "dos", "tres", "cuatro", "cinco");
$d = array_map(null, $a, $b, $c);
print_r($d);
?>
Das oben gezeigte Beispiel erzeugt folgende Ausgabe:
Array
(
[0] => Array
(
[0] => 1
[1] => eins
[2] => uno
)
[1] => Array
(
[0] => 2
[1] => zwei
[2] => dos
)
[2] => Array
(
[0] => 3
[1] => drei
[2] => tres
)
[3] => Array
(
[0] => 4
[1] => vier
[2] => cuatro
)
[4] => Array
(
[0] => 5
[1] => fünf
[2] => cinco
)
)
Wenn das Array-Argument String-Schlüssel enthält, wird das zurückgegebene Array String-Schlüssel enthalten sofern genau ein Array übergeben wurde. Sollten mehrere Arrays übergeben werden, so hat das zurückgegebene Array immer Integer-Schlüssel.
Beispiel #5 array_map() - mit String-Schlüsseln
<?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));
?>
Das oben gezeigte Beispiel erzeugt folgende Ausgabe:
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"
}
}
If you're looking for a way to flatten multimaps, look at this:
<?php
$multimap = array(
array("name"=>"value1"),
array("name"=>"value2"),
array("name"=>"value3")
);
$flatmap = array_map("array_pop",$multimap);
print_r($flatmap);
?>
Output:
Array
(
[0] => value1
[1] => value2
[2] => value3
)
Something that had me confused:
<?php
namespace test;
class Callback
{
static function add($a) { return $a + 1; }
}
$array = array(0, 1, 2);
array_map(array('Callback', 'add'), $array); // will not work, even though you're calling this in the test namespace
array_map(array('test\Callback', 'add'), $array); // will work
?>
PHP 5.3 enables us to use inline anonymous functions with array_map, cleaning up the syntax slightly.
<?php
$data = array(
array('id' => 1, 'name' => 'Bob', 'position' => 'Clerk'),
array('id' => 2, 'name' => 'Alan', 'position' => 'Manager'),
array('id' => 3, 'name' => 'James', 'position' => 'Director')
);
$names = array_map(
function($person) { return $person['name']; },
$data
);
print_r($names);
?>
This was possible (although not recommended) in prior versions of PHP 5, via create_function().
<?php
$names = array_map(
create_function('$person', 'return $person["name"];'),
$data
);
?>
You're less likely to catch errors in the latter version because the code is passed as string arguments.
These are alternatives to using a foreach:
<?php
$names = array();
foreach ($data as $row) {
$names[] = $row['name'];
}
?>
I realize this function is easy enough to make, but this is a faster version (twice the speed) of [a function] which I find incredibly useful.
<?php
function array_pluck($key, $input) {
if (is_array($key) || !is_array($input)) return array();
$array = array();
foreach($input as $v) {
if(array_key_exists($key, $v)) $array[]=$v[$key];
}
return $array;
}
?>
Usage:
<?php $ids = array_pluck('id', $users); ?>
Fixed a bug with array recursion.
<?php
/**
* arrayMap function. Customized array_map function which preserves keys/associate array indexes. Note that this costs a descent amount more memory (eg. 1.5k per call)
*
* @access public
* @param callback $callback Callback function to run for each element in each array.
* @param mixed $arr1 An array to run through the callback function.
* @param array $array Variable list of array arugments to run through the callback function.
* @return array Array containing all the elements of $arr1 after applying the callback function to each one, recursively, maintain keys.
*/
function arrayMap($callback,$arr1) {
$results = array();
$args = array();
if(func_num_args()>2)
$args = (array) array_shift(array_slice(func_get_args(),2));
foreach($arr1 as $key=>$value) {
$temp = $args;
array_unshift($temp,$value);
if(is_array($value)) {
array_unshift($temp,$callback);
$results[$key] = call_user_func_array(array('self','arrayMap'),$temp);
} else {
$results[$key] = call_user_func_array($callback,$temp);
}
}
return $results;
}
?>
Wrote up my own key preservation function for array mapping. It allows n arguments to be passed, and should be easy enough to follow if you need to make any mods. If you've got any thoughts let me know.
<?php
/**
* arrayMap function. Customized array_map function which preserves keys/associate array indexes.
*
* @access public
* @param callback $callback Callback function to run for each element in each array.
* @param mixed $arr1 An array to run through the callback function.
* @param array $array Variable list of array arugments to run through the callback function.
* @return array Array containing all the elements of $arr1 after applying the callback function to each one, recursively, maintain keys.
*/
function arrayMap($callback,$arr1) {
$results = array();
$args = array();
if(func_num_args()>2)
$args = (array) array_shift(array_slice(func_get_args(),2));
foreach($arr1 as $key=>$value) {
if(is_array($value)) {
array_unshift($args,$value);
array_unshift($args,$callback);
$results[$key] = call_user_func_array(array('self','arrayMap'),$args);
}
else {
array_unshift($args,$value);
$results[$key] = call_user_func_array($callback,$args);
}
}
return $results;
}
?>
I recently discovered that PHP has no loop-free manner for modifying the keys in an array. I was hoping to use a built-in function to prefix the keys.
Having found no native function to do this, I threw together this monster:
<?php
function array_prefix_keys ()
{
$args = func_get_args();
$prefix = array_shift($args);
$func = create_function('$p,$k','return "$p{$k}";');
foreach ($args AS $key => $array):
$args[$key] = array_combine( array_map( $func
, array_fill(0,count($array),$prefix)
, array_keys($array)
)
, array_values($array)
);
endforeach;
return $args;
}
$array1 = array(
'id' => 1,
'title' => 'about-us',
'author' => 'Bill Brown',
'dated' => '2009-SEP-15'
);
$array2 = array(
'id' => 2,
'title' => 'about-them',
'author' => 'Bill Smith',
'dated' => '2010-SEP-15'
);
echo '<pre>',print_r($array1,1),print_r($array2,1),'</pre>';
$array = array_prefix_keys("content_",$array1,$array2);
$array1 = $array[0];
$array2 = $array[1];
echo '<pre>',print_r($array1,1),print_r($array2,1),'</pre>';
?>
This will produce the following output:
Array
(
[id] => 1
[title] => about-us
[author] => Bill Brown
[dated] => 2009-SEP-15
)
Array
(
[id] => 2
[title] => about-them
[author] => Bill Smith
[dated] => 2010-SEP-15
)
Array
(
[content_id] => 1
[content_title] => about-us
[content_author] => Bill Brown
[content_dated] => 2009-SEP-15
)
Array
(
[content_id] => 2
[content_title] => about-them
[content_author] => Bill Smith
[content_dated] => 2010-SEP-15
)
Hope it helps!
Bill
[EDIT BY danbrown AT php DOT net: The original function and note was removed in favor of this update by the original author. The original note also contained the following descriptive text.]
I recently discovered that PHP has no loop-free manner for modifying the keys in an array. I was hoping to use a built-in function to prefix the keys.
Having found no native function to do this, I threw together this monster.
My English is weak but I want to share my code.
I want to change formation of array but when I use null is callback function in array_map().
It has problem in result so I write new small function for it.
<?php
function array_change_formation($arr=array()) {
$new_arr = array();
foreach($arr as $k => $v)
foreach($v as $k2 => $v2)
$new_arr[$k2][$k] = $v[$k2];
return $new_arr;
}
?>
Input:
Array
(
[Human] => Array
(
[0] => 1
[1] => 2
[2] => 3
[3] => 4
)
[Pet] => Array
(
[0] => Cat
[1] => Dog
[2] => Rabbit
[3] => Rat
)
)
OutPut:
Array
(
[0] => Array
(
[Human] => 1
[Pet] => Cat
)
[1] => Array
(
[Human] => 2
[Pet] => Dog
)
[2] => Array
(
[Human] => 3
[Pet] => Rabbit
)
[3] => Array
(
[Human] => 4
[Pet] => Rat
)
)
I hope it can useful.
Another way to array_map htmlentities with a specific quote style is to create a function that does it and map that function
<?php
function map_entities( $str ) {
return htmlentities( $str, ENT_QUOTES );
}
$good_array = array_map ( 'map_entities', $bad_array );
?>
To transpose rectangular two-dimension array, use the following code:
array_unshift($array, null);
$array = call_user_func_array("array_map", $array);
If you need to rotate rectangular two-dimension array on 90 degree, add the following line before or after (depending on the rotation direction you need) the code above:
$array = array_reverse($array);
Here is example:
<?php
$a = array(
array(1, 2, 3),
array(4, 5, 6));
array_unshift($a, null);
$a = call_user_func_array("array_map", $a);
print_r($a);
?>
Output:
Array
(
[0] => Array
(
[0] => 1
[1] => 4
)
[1] => Array
(
[0] => 2
[1] => 5
)
[2] => Array
(
[0] => 3
[1] => 6
)
)
You can easily remove all HTML tags from $_GET or $_POST variables using something like this:
<?php
$_POST = array_map('strip_tags', $_POST);
$_GET = array_map('strip_tags', $_GET);
?>
This is useful when you don't want to parse HTML.
If you want to pass an argument like ENT_QUOTES to htmlentities, you can do the follow.
<?php
$array = array_map( 'htmlentities' , $array, array_fill(0 , count($array) , ENT_QUOTES) );
?>
The third argument creates an equal sized array of $array filled with the parameter you want to give with your callback function.
The following takes an array of objects, and returns the result of calling a member function on each object. So if I have an array of objects that all have a getName() method, calling array_map_objects("getName", $thingies) will return the array filled with the getName() value for each object.
<?php
function array_map_objects($member_function, $array) {
$values = array();
if(is_string($member_function) && is_array($array)) {
$callback = create_function('$e', 'return call_user_func(array($e, "' . $member_function .'"));');
$values = array_map($callback, $array);
}
return $values;
}
?>
Here is a simple way to highlight the matched words in the search results:
<?php
function highlight($word) {
static $num = 1;
return '<span class="word' . $num++ . '">' . $word . '</span>';
}
$text = "ala bala nica turska panica";
$search = "bala turska";
$words = explode(' ', $search);
echo str_replace($words, array_map("highlight", $words), $text);
Wish this was built in. Mimics Ruby and Prototype's array pluck function. Returns specific key/column from an array of objects.
<?php
function array_pluck($key, $array)
{
if (is_array($key) || !is_array($array)) return array();
$funct = create_function('$e', 'return is_array($e) && array_key_exists("'.$key.'",$e) ? $e["'. $key .'"] : null;');
return array_map($funct, $array);
}
// usage:
$a = array(array("id"=>10, "name"=>"joe"), array("id"=>11, "name"=>"bob"));
$ids = array_pluck("id", $a); // == array(10,11)
$names = array_pluck("name", $a); // == array("joe", "bob")
//works on non-keyed arrays also:
$a = array(array(3,4), array(5,6));
$col2 = array_pluck(1,$a); // == array(4,6) (grab 2nd column of data)
?>
I was miffed that array_map didn't have a way to pass values *and* keys to the callback, but then I realized I could do this:
function callback($k, $v) { ... }
array_map( "callback", array_keys($array), $array);
Could also use things like...
array_keys(); and array_values(); offcourse...
However it's just an example off recursion via this function..
Which I found pretty handy at times dealing with arrays..
could also use:
<?php
call_user_func(array($this, __FUNCTION), $args);
?>
or
<?php
call_user_fuc_array(array($this, __FUNCTION__), $array);
?>
or
<?php
class{
public function __construct($arg){
if(is_array($arg)){
new self($arg);
}
else{
echo $arg.'<br/>'.PHP_EOL;
}
}
}
?>
Anyway.. plenty off examples..
It was just an idea for others...
loaded67 at hotmail dot com, there is a little error in the add func params values.
Warning: Missing argument 2 for test::add(), called in /tmp/test.php on line 34 and defined in /tmp/test.php on line 6
Array => <br/>
now it runs...
<?php
class test{
//private $container = array();
final public function add($key, $value=NULL){
/* params values fix */
$value = $value==NULL?$key:$value;
/* recursion */
if(is_array($value)){
array_map(array($this, __FUNCTION__), array_keys($value), array_values($value));
}
/* procedural */
else{
echo $key.' => '.$value.'<br/>'.PHP_EOL;
// do stuff...
// if(!isset($this->container[$key])){
// $this->container[$key] = $value;
// }
//else{ // trigger_error() xor throw new Exception?
// echo 'allready exists!<br/>'.PHP_EOL;
//}
}
}
}
//
$array = array (
'one' => 'value1',
'two' => 'value2',
'three' => 'value3'
);
$t = new test;
$t->add($array);
?>
good luck!
this function is really nice for recursion in php!!!
example in a class:
<?php
class test{
//private $container = array();
final public function add($key, $value){
/* recursion */
if(is_array($value)){
array_map(array($this, __FUNCTION__), array_keys($value), array_values($value));
}
/* procedural */
else{
echo $key.' => '.$value.'<br/>'.PHP_EOL;
// do stuff...
// if(!isset($this->container[$key])){
// $this->container[$key] = $value;
// }
//else{ // trigger_error() xor throw new Exception?
// echo 'allready exists!<br/>'.PHP_EOL;
//}
}
}
}
//
$array = array (
'one' => 'value1',
'two' => 'value2',
'three' => 'value3'
);
$t = new test;
$t->add($array);
?>
you could easiely do this without a class too offcourse!
used in php 5.2.5
This function behaves exactly like array_map but additionally does not reject non-array arguments. Instead, it transforms them with the array_fill function to a constant valued array of required length according to the other array arguments (if any) and executes the original array_map function.
<?php
function array_map2() {
$args = func_get_args();
$callback = array_shift($args);
$args = array_map(
create_function('$a,$max','return is_array($a)? $a: array_fill(0,$max,$a);'),
$args,array_fill(0,count($args),array_reduce($args,
create_function('$v,$w','return max($v,is_array($w)? count($w): 1);'))));
array_unshift($args,$callback);
return call_user_func_array("array_map",$args);
}
?>
Example:
<?php
$get = "first=value1&second=value2&third=value3";
print_r(array_map2("explode","=",explode("&",$get)));
?>
would print out:
<?php
Array
(
[0] => Array
(
[0] => first
[1] => value1
)
[1] => Array
(
[0] => second
[1] => value2
)
[2] => Array
(
[0] => third
[1] => value3
)
)
?>
/pmf
Adding method support to function by Andref (multidimensionalArrayMap).
function array_map_r( $func, $arr )
{
$newArr = array();
foreach( $arr as $key => $value )
{
$newArr[ $key ] = ( is_array( $value ) ? array_map_r( $func, $value ) : ( is_array($func) ? call_user_func_array($func, $value) : $func( $value ) ) );
}
return $newArr;
}
array_map_r('function', array());
or
array_map_r(array('class', 'method'), array());
Maybe this one will be useful for someone:
function array_map_helper($mapper, $array) {
$mapper = preg_replace('/^return (.*?);$/', '$1', trim($mapper));
$result = array();
if (preg_match('/(\(?)(.*?)\s*=>\s*(.*?)(\)?)$/', $mapper, $matches)) {
list($full_found, $array_open, $left, $right, $array_close) = $matches;
if ($array_open && $array_close) {
$mapper = '$result[] = array' . $full_found . ';';
} else {
$mapper = '$result[' . $left . '] = ' . $right . ';';
}
} else {
$mapper = '$result[] = ' . $mapper . ';';
}
foreach ($array as $key => $value) {
eval($mapper);
}
return $result;
}
should be used like:
$array = array(array('foo' => 11, 'bar' => 22),
array('foo' => 111, 'bar' => 222),
array('foo' => 1111, 'bar' => 2222));
$mapped = array_map_helper('$value["foo"] => $value["bar"]', $array);
var_dump will give
array(3) {
[11]=>
int(22)
[111]=>
int(222)
[1111]=>
int(2222)
}
or
$mapped = array_map_helper('$value["foo"]', $array);
var_dump will give
array(3) {
[0]=>
int(11)
[1]=>
int(111)
[2]=>
int(1111)
}
or
$mapped = array_map_helper('$value["foo"] + $value["bar"] . " at position $key"', $array);
var_dump will give
array(3) {
[0]=>
string(16) "33 at position 0"
[1]=>
string(17) "333 at position 1"
[2]=>
string(18) "3333 at position 2"
}
A recursive way to handle multidimensional arrays:
<?php
function multidimensionalArrayMap( $func, $arr )
{
$newArr = array();
foreach( $arr as $key => $value )
{
$newArr[ $key ] = ( is_array( $value ) ? multidimensionalArrayMap( $func, $value ) : $func( $value ) );
}
return $newArr;
}
?>
Hi benjaminhill,
You can apply a method of a instantiated class to array_maps as follows:
class Maths {
function addOne($input) {
return ($input + 1);
}
}
$maths = new Maths();
$sum = array_map(array($maths, \\\'addOne\\\'), array(1, 2));
// where $maths is the object which has been instantiated before and addOne is its method without its own parameters
var_dump($sum);
The code fragment will return:
array
0 => 2
1 => 3
However, I love a syntax like this:
$sum = array_map($maths->addOne($this), array(1, 2));
where $this should be interpreted as each values extracted from the subsequent array, which in this case is array(1, 2).
This syntax reminds me of Javascript syntax.
PHP\\\'s callback mechanism should be improved.
Here's a function, very helpfull to me, that allows you to map your callback on mixed args.
<?php
function array_smart_map($callback) {
// Initialization
$args = func_get_args() ;
array_shift($args) ; // suppressing the callback
$result = array() ;
// Validating parameters
foreach($args as $key => $arg)
if(is_array($arg)) {
// the first array found gives the size of mapping and the keys that will be used for the resulting array
if(!isset($size)) {
$keys = array_keys($arg) ;
$size = count($arg) ;
// the others arrays must have the same dimension
} elseif(count($arg) != $size) {
return FALSE ;
}
// all keys are suppressed
$args[$key] = array_values($arg) ;
}
// doing the callback thing
if(!isset($size))
// if no arrays were found, returns the result of the callback in an array
$result[] = call_user_func_array($callback, $args) ;
else
for($i=0; $i<$size; $i++) {
$column = array() ;
foreach($args as $arg)
$column[] = ( is_array($arg) ? $arg[$i] : $arg ) ;
$result[$keys[$i]] = call_user_func_array($callback, $column) ;
}
return $result ;
}
?>
Trying with :
<?php
// $_GET is ?foo=bar1-bar2-bar3&bar=foo1
print_r(array_smart_map('explode', '-', $_GET)) ;
?>
Returns :
array(
[foo] => array(
0 => bar1
1 => bar2
2 => bar3
)
[bar] => array(
1 => foo1
)
)
You can pass values to array_map by reference, essentially allowing you to use it as you would array_walk with multiple arrays as parameters.
A trivial example:
<?php
$a = array(1,2,3,4,5);
$add_func = create_function('&$x, $y', '$x+=$y;');
array_map($add_func, $a, $a);
print_r($a);
?>
Array
(
[0] => 2
[1] => 4
[2] => 6
[3] => 8
[4] => 10
)
The following function does exaclty the same thing of array_map. However, maintains the same index of the input arrays
<?php
function array_map_keys($param1,$param2,$param3=NULL)
{
$res = array();
if ($param3 !== NULL)
{
foreach(array(2,3) as $p_name)
{
if (!is_array(${'param'.$p_name}))
{
trigger_error(__FUNCTION__.'(): Argument #'.$p_name.' should be an array',E_USER_WARNING);
return;
}
}
foreach($param2 as $key => $val)
{
$res[$key] = call_user_func($param1,$param2[$key],$param3[$key]);
}
}
else
{
if (!is_array($param2))
{
trigger_error(__FUNCTION__.'(): Argument #2 should be an array',E_USER_WARNING);
return;
}
foreach($param2 as $key => $val)
{
$res[$key] = call_user_func($param1,$param2[$key]);
}
}
return $res;
}
?>
For instance:
<?php
$arr1 = array(
'3' => 'a',
'4' => 'b',
'5' => 'c'
);
$arr2 = array(
'3' => 'd',
'4' => 'e',
'5' => 'f'
);
$arr3 = array_map_keys(create_function('$a,$b','return $a.$b;'),$arr1,$arr2);
print_r($arr3);
?>
The result will be:
Array
(
[3] => ad
[4] => be
[5] => cf
)
If you need to call a static method from array_map, this will NOT work:
<?PHP
array_map('myclass::myMethod' , $value);
?>
Instead, you need to do this:
<?PHP
array_map( array('myclass','myMethod') , $value);
?>
It is helpful to remember that this will work with any PHP function which expects a callback argument.
array_map works also fine with create_function:
<?php
$a = array(1, 2, 3, 4, 5);
$b = array_map(create_function('$n', 'return $n*$n*$n;'), $a);
print_r($b);
?>
if you want to manipulate the elements of the array, instead to on a copy,
than take a look at array_walk:
<?php
$a = array(1, 2, 3, 4, 5);
array_walk($a, create_function('&$n', '$n = $n*$n*$n;'));
print_r($a);
?>
The Result of both is:
Array
(
[0] => 1
[1] => 8
[2] => 27
[3] => 64
[4] => 125
)
Occasionally, you may find that you need to pull out a column (or several) from an array. Here's a map-like function to do that:
<?php
function &array_shear(&$arrays, $idx1 /* ... */) {
$indexes = func_get_args();
array_shift($indexes);
$newArrays = array ();
foreach (array_keys($arrays) as $arrayKey) {
$newArray = array ();
foreach ($indexes as $index) {
$newArray[$index] = $arrays[$arrayKey][$index];
unset($arrays[$arrayKey][$index]);
}
$newArrays[$arrayKey] = $newArray;
}
return $newArrays;
}
?>
So, doing this:
<?php
$t1 = array (
2 => array ('a', 'b', 'c'),
1 => array ('d', 'e', 'f'),
5 => array ('g', 'h', 'i'),
);
$t2 = array_shear($t1, 1, 0);
?>
will result in:
<?php
$t1 = array (
2 => array ( 2 => 'c', ),
1 => array ( 2 => 'f', ),
5 => array ( 2 => 'i', ),
);
$t2 = array (
2 => array ( 1 => 'b', 0 => 'a', ),
1 => array ( 1 => 'e', 0 => 'd', ),
5 => array ( 1 => 'h', 0 => 'g', ),
);
?>
A note when doing something allong the lines of:
<?php
class foo {
var $var;
function bar() {
array_map(array($this, "baz"), array(1,2,3));
}
function baz($arg) {
$this->var = $this->var + $arg;
}
}
?>
This will *not* work as expected. You need to pass $this by reference as with:
array_map(array(&$this, "baz"), array(1,2,3));
or you'll be making a copy of the object each time, changing a value, then throwing the result away.
Here is a better, more true version of a deep array_map. The only negative of this function is that the array is passed by reference, so just be aware of that. (patches welcome)
<?php
function array_map_deep(&$in_array, $in_func, $in_args = array(), $in_index = 1) {
// fix people from messing up the index of the value
if ($in_index < 1) {
$in_index = 1;
}
foreach (array_keys($in_array) as $key) {
// we need a reference, not a copy, normal foreach won't do
$value =& $in_array[$key];
// we need to copy args because we are doing
// manipulation on it farther down
$args = $in_args;
if (is_array($value)) {
array_map_deep($value, $in_func, $in_args, $in_index);
}
else {
array_splice($args, $in_index - 1, $in_index - 1, $value);
$value = call_user_func_array($in_func, $args);
}
}
return $in_array;
}
?>
This is a neat function because you can pass an array, a function, and an array of parameters, and finally, and index of where in the array of parameters for the callback function the contents you are mapping should get replaced. This index is human based (starts at 1), and can be used in something like a preg_replace callback, where the contents must be the 3rd index. Enjoy!
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