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array_map

(PHP 4 >= 4.0.6, PHP 5, PHP 7)

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: 对每个数组的每个元素作用的回调函数。
arr1: 将被回调函数（callback）执行的数组。
array: 将被回调函数（callback）执行的数组列表。

返回值

返回一个数组，该数组的每个元素都数组（arr1）里面的每个元素经过回调函数（callback）处理了的。

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
        ))

如果数组参数里面有字符串的键，那么返回的数组就会包含字符串的键，仅且仅当只传入一个数组的时候（试了下，就是原数组返回，没变化啊，这不是蛋疼么？）。如果不止一个数组被传入，那么返回的数组的的键都是整型。

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() - 使用用户自定义函数对数组中的每个元素做回调处理
create_function() - Create an anonymous (lambda-style) function
callback 类型的信息

用户评论:

[#1] shabeerksbr at hotmail dot com [2015-10-22 19:50:36]

[#2] Mahn [2015-10-20 17:10:19]

You may be looking for a method to extract values of a multidimensional array on a conditional basis (i.e. a mixture between array_map and array_filter) other than a for/foreach loop. If so, you can take advantage of the fact that 1) the callback method on array_map returns null if no explicit return value is specified (as with everything else) and 2) array_filter with no arguments removes falsy values.

So for example, provided you have:

<?php $data = [ [ "name" => "John", "smoker" => false ], [ "name" => "Mary", "smoker" => true ], [ "name" => "Peter", "smoker" => false ], [ "name" => "Tony", "smoker" => true ] ]; ?>

You can extract the names of all the non-smokers with the following one-liner:

<?php $names = array_filter(array_map(function($n) { if(!$n['smoker']) return $n['name']; }, $data)); ?>

It's not necessarily better than a for/foreach loop, but the occasional one-liner for trivial tasks can help keep your code cleaner.

[#3] info at katoba dot de [2015-10-02 12:08:27]

Maybe usefull: replace a string in all array-elements
<?php $hayStack = ["Book :id","Car :id","Cat :id"]; $replaced = array_map(function($element) use ($replace){ return str_replace(":id",$replace,$element); },$hayStack); print_r($replaced); ?>

[#4] nelf86 at gmail dot com [2015-08-13 11:10:46]

Here is how to perform an operation on some of the elements of an array:

<?php $an_array = array( 'item1' => 0, 'item2' => 0, 'item3' => 0, 'item4' => 0, 'item5' => 0, ); $items_to_modify = array('item1', "item3"); array_map(function ($value) use (&$an_array ) { $an_array [$value] = (boolean)$an_array [$value]; //example operation: }, $items_to_modify); ?>

This will take the original array and perform an action only on items specified on the second array items. Use of & symbol in the use statement makes the array_map access the variable as a reference in an outer scope.

This makes code easily extendable.

[#5] CertaiN [2015-03-24 17:15:55]

Simplest array_map_recursive() implemention.

<?php function array_map_recursive(callable $func, array $array) { return filter_var($array, \FILTER_CALLBACK, ['options' => $func]); } ?>

[#6] mark at grooveshark dot com [2015-01-20 04:44:26]

If you're looking for a way to get a specific set of key values (ala "pluck") you can just use array_column([['id' => 1]], 'id').

[#7] wapinet at mail dot ru [2014-07-15 13:54:40]

PHP 5.5.14
<?php
$columns = range(1, 100000);
$time = microtime(true);

array_map(function ($value) {
    return 'p.' . $value;
}, $columns);

foreach ($columns as $key => $column) {
    $columns[$key] = 'p.' . $column;
}

array_walk($columns, function (&$value, $key) {
    $value = 'p.' . $value;
});

foreach ($columns as &$column) {
    $column = 'p.' . $column;
}

echo microtime(true) - $time . "\n" . memory_get_peak_usage(true) . "\n";

[#8] JacobA dot Barber at yahoo dot com [2014-05-07 16:27:04]

Here is an example for php 5.4 and greater, using a closure:
<?php $myList = [1,2,3,4]; $mappedList = array_map(function($value){ return $value * 2; }, $myList); var_dump($mappedList); array(4) { [0]=>int(2) [1]=>int(4) [2]=>int(6) [3]=>int(8) } ?>
This is useful when you don't want/need to define a function just so it can be used with the map function.

[#9] ian_channing at hotmail dot com [2014-02-12 11:10:06]

I wanted a nice way to convert an array with x values as keys and y values as values e.g. array(x => y,...) into x,y co-ordinates e.g. array(array(x,y), ...).

You can do:

<?php foreach ($waveform as $key => $waveformPoint) { $coordinates[] = array($key, $waveformPoint); } ?>

But array_map with a null callback gives you a nicer way:

<?php $coordinates = array_map(null, array_keys($waveform), array_values($waveform)); ?>

[#10] williamprogphp at yahoo dot com dot br [2014-01-31 12:54:33]

A function to map an array working also with its key.

<?php function array_mapk($callback, $array) { $newArray = array(); foreach ($array as $k => $v) { $newArray[$k] = call_user_func($callback, $k, $v); } return $newArray; } ?>

Usage:

<?php $dados = array(); $dados['cep'] = "32340-070"; $dados['initial'] = 100; $dados['final'] = 300; $dados['processed'] = 1; echo "update table set " . implode(", ", array_mapk(function ($k, $v) { return "{$k} = '" . mysql_real_escape_string($v) . "'"; }, $dados)); ?>

Cheers.

[#11] elfe1021 at gmail dot com [2013-12-13 02:44:20]

Find an interesting thing that in array_map's callable function, late static binding does not work:
<?php class A {     public static function foo($name) {         return 'In A: '.$name;     }     public static function test($names) {         return array_map(function($n) {return static::foo($n);}, $names);     } } class B extends A{     public static function foo($name) {         return 'In B: '.$name;     } } $result = B::test(['alice', 'bob']); var_dump($result); ?>

the result is:
array (size=2)
  0 => string 'In A: alice' (length=11)
  1 => string 'In A: bob' (length=9)

if I change A::test to
<?php     public static function test($names) {         return array_map([get_called_class(), 'foo'], $names);     } ?>

Then the result is as expected:
array (size=2)
  0 => string 'In B: alice' (length=11)
  1 => string 'In B: bob' (length=9)

[#12] lukasz dot mordawski at gmail dot com [2013-12-03 10:55:39]

Let's assume we have following situation:

<?php class MyFilterClass { public function filter(array $arr) { return array_map(function($value) { return $this->privateFilterMethod($value); }); } private function privateFilterMethod($value) { if (is_numeric($value)) $value++; else $value .= '.'; } } ?>

This will work, because $this inside anonymous function (unlike for example javascript) is the instance of MyFilterClass inside which we called it.
I hope this would be useful for anyone.

[#13] CertaiN [2013-08-22 20:52:36]

The most memory-efficient array_map_recursive().

<?php function array_map_recursive(callable $func, array $arr) { array_walk_recursive($arr, function(&$v) use ($func) { $v = $func($v); }); return $arr; } ?>

[#14] contato at williamsantana dot com dot br [2013-07-30 12:42:32]

In case of you need to recursively bypass a function over the itens of an array, you can use it

<?php     function array_map_recursive($callback, $array) {         foreach ($array as $key => $value) {             if (is_array($array[$key])) {                 $array[$key] = array_map_recursive($callback, $array[$key]);             }             else {                 $array[$key] = call_user_func($callback, $array[$key]);             }         }         return $array;     } ?>

-----------------------------------------------------------------------

<?php     $strings = array(         'The',         array(             'quick',             'fox',             array(                 'brown',                 'jumps',                 array(                     'over',                     array(                         'the',                         array(                             'lazy',                             array(                                 'dog'                             )                         )                     )                 )             )         )     );     print_r($strings);     $hashedString = array_map_recursive('md5', $strings);     print_r($hashedString); ?>

------------------------------------------------------------------------
Testing it, you'll obtain

<?php array (   0 => 'The',   1 =>   array (     0 => 'quick',     1 => 'fox',     2 =>     array (       0 => 'brown',       1 => 'jumps',       2 =>       array (         0 => 'over',         1 =>         array (           0 => 'the',           1 =>           array (             0 => 'lazy',             1 =>             array (               0 => 'dog',             ),           ),         ),       ),     ),   ), ); array (   0 => 'a4704fd35f0308287f2937ba3eccf5fe',   1 =>   array (     0 => '1df3746a4728276afdc24f828186f73a',     1 => '2b95d1f09b8b66c5c43622a4d9ec9a04',     2 =>     array (       0 => '6ff47afa5dc7daa42cc705a03fca8a9b',       1 => '55947829059f255e4ba2f536a2ae99fe',       2 =>       array (         0 => '3b759a9ca80234563d87672350659b2b',         1 =>         array (           0 => '8fc42c6ddf9966db3b09e84365034357',           1 =>           array (             0 => '0ffe34b4e04c2b282c5a388b1ad8aa7a',             1 =>             array (               0 => '06d80eb0c50b49a509b49f2424e8c805',             ),           ),         ),       ),     ),   ), ); ?>

Hope it helps you.

Cheers.

[#15] jessiedeer at hotmail dot com [2013-07-16 10:34:52]

array_map becomes interesting and faster than foreach when used with existing PHP functions.

Example:

$arr1 = array(1, 2, 3, 4);
$arr2 = array(4, 3, 2, 1);

// array with min values for each key
print_r(array_map("min", $arr1, $arr2));

Result: Array ( [0] => 1 [1] => 2 [2] => 2 [3] => 1 )

// array with max values for each key
print_r(array_map("max", $arr1, $arr2));

Result: Array ( [0] => 4 [1] => 3 [2] => 3 [3] => 4 )

[#16] jessiedeer at hotmail dot com [2013-07-16 10:27:30]

[#17] Anonymous [2013-07-06 01:21:44]

Simple yet effective associative version of map that accepts arbitrary number of arrays.
Instead of elements, result from each() get passed as function arguments.

<?php
function array_map_assoc(){
    if(func_num_args() < 2) throw new \BadFuncionCallException('Missing parameters');
    $args = func_get_args();
    $callback = $args[0];
    if(!is_callable($callback)) throw new \InvalidArgumentException('First parameter musst be callable');
    $arrays = array_slice($args, 1);
    array_walk($arrays, function(&$a){
        $a = (array)$a;
        reset($a);
    });
    $results = array();
    $max_length = max(array_map('count', $arrays));
    $arrays = array_map(function($pole) use ($max_length){
        return array_pad($pole, $max_length, null);
    }, $arrays);
    for($i=0; $i < $max_length; $i++){
        $elements = array();
        foreach($arrays as &$v){
            $elements[] = each($v);
        }
        unset($v);
        $out = call_user_func_array($callback, $elements);
        if($out === null) continue;
        $val = isset($out[1]) ? $out[1] : null;
        if(isset($out[0])){
            $results[$out[0]] = $val;
        }else{
            $results[] = $val;
        }
    }
    return $results;
}

//USAGE:
$days = array('Sun' => 'Sunday', 'Mon' => 'Monday', 'Tue' => 'Tuesday', 'Wed' => 'Wednesday', 'Thu' => 'Thursday', 'Fri' => 'Friday', 'Sat' => 'Saturday');
$nums = array('First', 'Second', 'Third', 'Fourth', 'Fifth', 'Sixth', 'Seventh');

$result = array_map_assoc(function($a, $b){
    return array($b['value'], $a['key']);
}, $days, $nums);

var_dump($result);

//RESULT:
array (size=7)
  'First' => string 'Sun' (length=3)
  'Second' => string 'Mon' (length=3)
  'Third' => string 'Tue' (length=3)
  'Fourth' => string 'Wed' (length=3)
  'Fifth' => string 'Thu' (length=3)
  'Sixth' => string 'Fri' (length=3)
  'Seventh' => string 'Sat' (length=3)

[#18] hrvoj3e at gmail dot com [2013-04-30 14:38:42]

Why not use

mb_convert_case($str, MB_CASE_TITLE, "UTF-8");

Works for me! :)

[#19] James [2013-03-15 17:07:05]

array_map() can be applied to assoc arrays without affecting the keys

[#20] shakespeare32 at gmail dot com [2013-02-19 19:01:38]

Why not an array of callbacks?

<?php function array_maps($callbacks, $array) { if (!$callbacks) { return $array; } if (!is_array($callbacks) && is_string($callbacks) && function_exists($callbacks)) { return array_map($callbacks, $array); } foreach($callbacks as $callback) { if (function_exists($callback)) { $array = array_map($callback, $array); } } return $array; } ?>

[#21] godek dot maciek at gmail dot com [2012-04-19 07:01:43]

I came up with a convenient syntax for method application, particularly useful inside the array_map.
For instance, if you want to
array_map(function($object, $arg1) { return $object->method($arg1, "arg2"); }, $objects, $args1);

it is possible to provide a shorthand:
global $_; // necessary inside a function, unfortunately

array_map($_->method($_, "arg2"), $objects, $args1);

Here's the implementation (works with 5.3)

function m_caller($method) {
  $args = func_get_args();
  array_shift($args);
  return function($object) use($method, $args) {
    global $_;
    $local_args = func_get_args();
    array_shift($args);
    if(!is_object($object)) {
      // error
    }
    $reflection = new ReflectionMethod(get_class($object), $method);
    foreach($args as $key => $arg) {
      if($arg === $_) {
        $args[$key] = array_shift($local_args);
      }
    }
    return $reflection->invokeArgs($object, array_merge($args, $local_args));
  };
}

class MethodCaller {
  public function __call($name, $arguments) { return call_user_func_array('m_caller', array_merge(array($name), $arguments)); }
  public function __get($name) { return m_caller($name); }
};

$_ = new MethodCaller();

[#22] qeremy [2012-03-07 10:35:00]

An alternative for recursive mapping;

<?php function array_map_recursive($fn, $arr) {     $rarr = array();     foreach ($arr as $k => $v) {         $rarr[$k] = is_array($v)             ? array_map_recursive($fn, $v)             : $fn($v); // or call_user_func($fn, $v)     }     return $rarr; } function sqr($x) {     return "$x ^ 2 = ". ($x * $x); } $a = array(1, 2, 3, array(4, array(5))); $b = array_map_recursive("sqr", $a); print_r($b); ?>

Array
(
    [0] => 1 ^ 2 = 1
    [1] => 2 ^ 2 = 4
    [2] => 3 ^ 2 = 9
    [3] => Array
        (
            [0] => 4 ^ 2 = 16
            [1] => Array
                (
                    [0] => 5 ^ 2 = 25
                )

        )

)

[#23] gmail.com@mspreij [2012-02-26 22:48:19]

Hope I'm not late to the party, here's my function to apply array_map to the *keys* of an array.
Extra array arguments will be used for the callback function's parameters just like with array_map, with the difference that a string is also allowed: it will just be used to create an array of appropriate length with as each value that string. Arrays are left alone (and will be padded with nulls by array_map as needed).

<?php //_________________________________________________ // array_map_keys($callback, $array, [$args, ..]) / function array_map_keys($callback, $array ) { $args = func_get_args(); if (! is_callable($callback)) trigger_error("first argument (callback) is not a valid function", E_USER_ERROR); if (! is_array($array)) trigger_error("second argument must be an array", E_USER_ERROR); $args[1] = array_keys($array); // If any additional arguments are not arrays, assume that value is wanted for every $array item. // array_map() will pad shorter arrays with Null values for ($i=2; $i < count($args); $i++) { if (! is_array($args[$i])) { $args[$i] = array_fill(0, count($array), $args[$i]); } } return array_combine(call_user_func_array('array_map', $args), $array); } // Some examples: $arr = array('foo'=>123, 'bar'=>456); // simply uppercase keys: var_dump(array_map_keys('strtoupper', $arr)); // or.. var_dump(array_map_keys(function($input) {return strtoupper($input);}, $arr)); // >> array(2) { ["FOO"]=>int(123) , ["BAR"]=> int(456) } // Add a prefix 'myvar_': var_dump(array_map_keys(function($input, $prefix) {return $prefix.$input;}, $arr, 'myvar_')); // >> array(2) { ["myvar_foo"]=>int(123) , ["myvar_bar"]=>int(456) } // Apart from the (static string) prefix, we also number them: $arr = array('foo'=>123, 'bar'=>456, 'bazz'=>789, 'yadda'=>'0AB'); var_dump(array_map_keys(function($input, $middle, $number) {return $number.':'.$middle.$input;}, $arr, 'myvar_', range(1, count($arr)))); // >> array(4) { ["1:myvar_foo"]=>int(123) , ["2:myvar_bar"]=>int(456) , ["3:myvar_bazz"]=>int(789) , ["4:myvar_yadda"]=>string(3) "0AB" } ?>

[#24] php/hotblocks/nl [2011-11-28 05:00:17]

Note that the $arr argument has to be an array, not just a Traversable/Iterator.

For instance this won't work:

<?php $documents = $mongo->db->collection->find(); // $documents is Traversable by foreach $ids = array_map(function($document) { return $document['_id']; }, $objects); // $ids will now be NULL, because $documents wasn't an Array ?>

A solution is to first use iterator_to_array():

<?php $ids = array_map(function($document) { return $document['_id']; }, iterator_to_array($objects)); // $ids will now be an array of ['_id']s ?>

But this is not very efficient: two cycles instead of one. Another solution is to use foreach: one cycle and a lot of freedom (and in the same scope).

[#25] gordon dot mcvey at ntlworld dot com [2011-01-28 05:11:42]

You can use array_map with PHP native functions as well as user functions. This is very handy if you need to sanitize arrays.

<?php $integers = array_map ('intval', $integers); $safeStrings = array_map ('mysql_real_escape_string', $unsafeStrings); ?>

[#26] virtual dot greg at gmail dot com [2010-03-05 03:07:35]

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']; } ?>

[#27] kelly m [2010-02-17 14:28:28]

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); ?>

[#28] onassar at gmail dot com [2009-10-13 19:06:13]

Fixed a bug with array recursion.

<?php 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; } ?>

[#29] onassar at gmail dot com [2009-10-11 15:33:07]

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 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; } ?>

[#30] galenjr at gmail dot com [2009-06-14 23:19:50]

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 ); ?>

[#31] radist-hack at yandex dot ru [2008-11-01 13:37:35]

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
        )

)

[#32] Heero [2008-10-16 10:02:57]

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.

[#33] stijnleenknegt at gmail dot com [2008-07-22 16:17:11]

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.

[#34] GUI [2008-06-26 07:48:36]

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; } ?>

[#35] moester at gmail dot com [2008-04-02 13:21:38]

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) ?>

[#36] chreekat [2008-03-12 15:48:54]

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);

[#37] jo at ho dot nl [2008-02-17 14:10:46]

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...

[#38] loaded67 at hotmail dot com [2008-02-08 02:59:23]

this function is really nice for recursion in php!!!

example in a class:

<?php class test{ //private $container = array(); final public function add($key, $value){ if(is_array($value)){ array_map(array($this, __FUNCTION__), array_keys($value), array_values($value)); } 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

[#39] pmf [2008-01-22 19:02:13]

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

[#40] henrique at webcoder dot com dot br [2007-11-01 08:02:18]

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());

[#41] bturchik at iponweb dot net [2007-07-19 07:46:15]

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"
}

[#42] andref dot dias at pronus dot eng dot br [2006-10-24 12:14:17]

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; } ?>

[#43] pcdinh at phpvietnam dot net [2006-03-17 20:50:57]

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.

[#44] [2005-08-26 06:57:43]

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
    )
)

[#45] david dot tulloh at infaze dot com dot au [2005-07-06 16:53:52]

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
)

[#46] Vinicius Cubas Brand [2005-03-23 05:31:01]

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
)

[#47] endofyourself at yahoo dot com [2005-02-19 23:29:40]

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.

[#48] nd0 at gmx dot de [2004-07-02 04:42:52]

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
)

[#49] stephen at mu dot com dot au [2003-01-06 22:02:12]

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.

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