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array_walk

(PHP 4, PHP 5, PHP 7, PHP 8)

array_walk — 配列の全ての要素にユーザー定義の関数を適用する

説明

array_walk(array|object &$array, callable $callback, mixed $arg = null): bool

array 配列の各要素にユーザー定義関数 callback を適用します。

array_walk() は array の内部配列ポインタに影響されません。array_walk() はポインタの位置に関わらず配列の全てに渡って適用されます。

パラメータ

array

入力の配列。

callback

通常、 callback は引数を二つとります。 array パラメータの値が最初の引数、キー/添字は二番目の引数となります。

注意:
callback により配列の値そのものを変更する必要がある場合、 callback の最初の引数はリファレンスとして渡す必要があります。この場合、配列の要素に加えた変更は、配列自体に対して行われます。

注意:
内部関数の多く (たとえば strtolower()) は、期待しているよりも多い引数を受け取ると警告が発生します。そのため、callback に直接指定することはできません。

変更される可能性があるのは配列の値だけであり、その構造を変更することはできません。つまり、プログラマは要素の追加や削除そして並べ替えなどができないということです。コールバック関数がこの条件を満たさない場合は、この関数の動作は未定義で予期せぬ結果を得ることになります。

arg

オプションの arg パラメータが指定された場合、コールバック関数 callback への三番目の引数として渡されます。

戻り値

true を返します。

エラー / 例外

PHP 7.1.0 以降では、callback 関数が 2個より多いパラメータ（配列メンバーの値およびキー）を必要とする場合、または、(arg も渡されている場合) 3個より多いパラメータを必要とする場合、 ArgumentCountError がスローされます。 7.1.0 より前のバージョンでは、callback 関数が 2 つより多いパラメータを必要とする場合、 array_walk() が callback をコールする度にエラーレベル E_WARNING が発生させていました。

変更履歴

バージョン	説明
8.0.0	`callback` が、 2番目と3番目の引数にリファレンス渡しされる引数を期待している場合、この関数は `E_WARNING` を発生させるようになりました。

例

例1 array_walk() の例

<?php
$fruits = array("d" => "lemon", "a" => "orange", "b" => "banana", "c" => "apple");

function test_alter(&$item1, $key, $prefix)
{
    $item1 = "$prefix: $item1";
}

function test_print($item2, $key)
{
    echo "$key. $item2\n";
}

echo "Before ...:\n";
array_walk($fruits, 'test_print');

array_walk($fruits, 'test_alter', 'fruit');
echo "... and after:\n";

array_walk($fruits, 'test_print');
?>

上の例の出力は以下となります。

Before ...:
d. lemon
a. orange
b. banana
c. apple
... and after:
d. fruit: lemon
a. fruit: orange
b. fruit: banana
c. fruit: apple

例2 無名関数を使った、array_walk() の例

<?php
$elements = ['a', 'b', 'c'];

array_walk($elements, function ($value, $key) {
  echo "{$key} => {$value}\n";
});

?>

上の例の出力は以下となります。

0 => a
1 => b
2 => c

参考

array_walk_recursive() - 配列の全ての要素に、ユーザー関数を再帰的に適用する
iterator_apply() - ユーザー関数をイテレータのすべての要素でコールする
list() - 配列と同様の形式で、複数の変数への代入を行う
each() - 配列から現在のキーと値のペアを返して、カーソルを進める
call_user_func_array() - パラメータの配列を指定してコールバック関数をコールする
array_map() - 指定した配列の要素にコールバック関数を適用する
foreach

add a note

User Contributed Notes 37 notes

down

243

bisqwit at iki dot fi ¶

20 years ago


It's worth nothing that array_walk can not be used to change keys in the array.
The function may be defined as (&$value, $key) but not (&$value, &$key).
Even though PHP does not complain/warn, it does not modify the key.

down

ezhacher at gmail dot com ¶

10 years ago


Calling an array Walk inside a class 

If the class is static:
array_walk($array, array('self', 'walkFunction'));
or
array_walk($array, array('className', 'walkFunction'));

Otherwise:
array_walk($array, array($this, 'walkFunction'));

down

01001coder at gmail dot com ¶

6 years ago


I noticed that :

PHP ignored arguments type when using array_walk() even if there was
 
declare(strict_types=1) . 

See this code as an example ...

<?php
declare(strict_types=1);

$fruits = array("butter" => 5.3, "meat" => 7, "banana" => 3);

function test_print(int $item2, $key) {
    echo "$key: $item2<br />\n";
}

array_walk($fruits, 'test_print');

?>

The output is :

butter: 5
meat: 7
banana: 3

whilst the expecting output is :

Fatal error: Uncaught TypeError: Argument 1 passed to test_print() must be of the type integer

because "butter" => 5.3 is float

I asked someone about it and they said "this was caused by the fact that callbacks called from internal code will always use weak type". But I tried to do some tests and this behavior is not an issue when using call_user_func().

down

fred ¶

8 years ago


Correction for the speed test from zlobnygrif.

<?php
// Test results
$array1 = test('array_walk');
$array2 = test('array_walk_list_each');
$array3 = test('array_walk_foreach1');
$array4 = test('array_walk_foreach2');

// Check arrays for equal
var_dump($array1 == $array2, $array1 == $array3, $array1 == $array4);

// Test function 1
function array_walk_list_each(&$array, $function, $userData = null) {
   /* make sure we walk the array each time */
    reset($array);
    while ( list($key, $value) = each($array) )
        $function($array[$key], $key, $userData);
}

// Test function 2
function array_walk_foreach1(&$array, $function, $userData = null) {
    foreach ($array as $key => &$value )
        $function($value, $key, $userData);
}

// Test function 3
function array_walk_foreach2(&$array, $function, $userData = null) {
    foreach ($array as $key => $value )
        $function($array[$key], $key, $userData);
}

function some_function(&$value, $key, $userData) {
    $value = "$key => $userData";
}

function test($function, $count = 10000, $arrayElements = 1000) {
    echo $function, ' ... ';
    $array = array_fill(0, $arrayElements, "some text value");
   
    $timer = microtime(true);
    for( $i = 0; ++$i < $count; )
        /* change data for each $i */
        $function($array, 'some_function', 'some user data ' . $i);
    printf("%.3f sec\n", microtime(true) - $timer);
   
    return $array;
}

down

ludvig dot ericson at gmail dot com ¶

19 years ago


In response to 'ibolmo', this is an extended version of string_walk, allowing to pass userdata (like array_walk) and to have the function edit the string in the same manner as array_walk allows, note now though that you have to pass a variable, since PHP cannot pass string literals by reference (logically).

<?php
function string_walk(&$string, $funcname, $userdata = null) {
    for($i = 0; $i < strlen($string); $i++) {
        # NOTE: PHP's dereference sucks, we have to do this.
        $hack = $string{$i};
        call_user_func($funcname, &$hack, $i, $userdata);
        $string{$i} = $hack;
    }
}

function yourFunc($value, $position) {
    echo $value . ' ';
}

function yourOtherFunc(&$value, $position) {
    $value = str_rot13($value);
}

# NOTE: We now need this ugly $x = hack.
string_walk($x = 'interesting', 'yourFunc');
// Ouput: i n t e r e s t i n g

string_walk($x = 'interesting', 'yourOtherFunc');
echo $x;
// Output: vagrerfgvat
?>

Also note that calling str_rot13() directly on $x would be much faster ;-) just a sample.

down

chaley at brtransport dot com ¶

10 years ago


There is a note about 3 years ago regarding using this for trimming. array_map() may be cleaner for this. I haven't checked the time/resource impact:

$result = array_map("trim", $array);

down

Maxim ¶

13 years ago


Note that using array_walk with intval is inappropriate.
There are many examples on internet that suggest to use following code to safely escape $_POST arrays of integers:
<?php
array_walk($_POST['something'],'intval'); // does nothing in PHP 5.3.3
?>
It works in _some_ older PHP versions (5.2), but is against specifications. Since intval() does not modify it's arguments, but returns modified result, the code above has no effect on the array and will leave security hole in your website.

You can use following instead:
<?php
$_POST['something'] = array_map(intval,$_POST['something']);
?>

down

rustamabd at gmail dot com ¶

14 years ago


Don't forget about the array_map() function, it may be easier to use!

Here's how to lower-case all elements in an array:

<?php
    $arr = array_map('strtolower', $arr);
?>

down

EllisGL ¶

6 years ago


For those that think they can't use array_walk to change / replace a key name, here you go:

<?php
function array_explore(array &$array, callable $callback)
{
    array_walk($array, function(&$value, $key) use (&$array, $callback)
    {
        $callback($array, $key, $value);

        if(is_array($value))
        {
            array_explore($value, $callback);
        }
    });
}

/**
 * Stolen from: https://stackoverflow.com/questions/13233405/change-key-in-associative-array-in-php
 */
function renameKey(array &$data, $oldKey, $newKey, $ignoreMissing = false, $replaceExisting = false)
{
    if (!empty($data))
    {
        if (!array_key_exists($oldKey, $data))
        {
            if ($ignoreMissing)
            {
                return FALSE;
            }

            throw new \Exception('Old key does not exist.');
        }
        else
        {
            if (array_key_exists($newKey, $data))
            {
                if ($replaceExisting)
                {
                    unset($data[$newKey]);
                }
                else
                {
                    throw new \Exception('New key already exist.');
                }
            }

            $keys = array_keys($data);
            
            // Fix from EllisGL: http://php.net/manual/en/function.array-search.php#122377
            $keys[array_search($oldKey, array_map('strval', $keys))] = $newKey;

            $data = array_combine($keys, $data);

            return TRUE;
        }
    }

    return FALSE;
}
    
$array = [
    "_10fish" => 'xyz',
    "_11fish" => [
        "_22" => "a", "b", "c"
        ],
    "someFish" => [
        'xyz',
        '@attributes' => ['type' => 'cod']
        ]
    ];

array_explore($array, function(&$value, $key)
{
    // Replace key '@attrutes' with '_attributes'
    if('@attributes' === $key)
    {
        renameKey($value, $key, '_attributes');
    }

});

print_r($array);
?>

down

erelsgl at gmail dot com ¶

15 years ago


If you want to unset elements from the callback function, maybe what you really need is array_filter.

down

Andrzej Martynowicz at gmail dot com ¶

19 years ago


It can be very useful to pass the third (optional) parameter by reference while modifying it permanently in callback function. This will cause passing modified parameter to next iteration of array_walk(). The exaple below enumerates items in the array:



<?php

function enumerate( &$item1, $key, &$startNum ) {

   $item1 = $startNum++ ." $item1";

}



$num = 1;



$fruits = array( "lemon", "orange", "banana", "apple");

array_walk($fruits, 'enumerate', $num );



print_r( $fruits );



echo '$num is: '. $num ."\n";

?>



This outputs:



Array

(

    [0] => 1 lemon

    [1] => 2 orange

    [2] => 3 banana

    [3] => 4 apple

)

$num is: 1



Notice at the last line of output that outside of array_walk() the $num parameter has initial value of 1. This is because array_walk() does not take the third parameter by reference.. so what if we pass the reference as the optional parameter..



<?php

$num = 1;



$fruits = array( "lemon", "orange", "banana", "apple");

array_walk($fruits, 'enumerate', &$num ); // reference here



print_r( $fruits );



echo '$num is: '. $num ."\n";

echo "we've got ". ($num - 1) ." fruits in the basket!";

?>

 

This outputs:

Array

(

    [0] => 1 lemon

    [1] => 2 orange

    [2] => 3 banana

    [3] => 4 apple

)

$num is: 5

we've got 4 fruits in the basket!



Now $num has changed so we are able to count the items (without calling count() unnecessarily).



As a conclusion, using references with array_walk() can be powerful toy but this should be done carefully since modifying third parameter outside the array_walk() is not always what we want.

down

taj at yahoo dot fr ¶

5 years ago


// We can make that with this simple FOREACH loop : 

$fruits = array("d" => "lemon", "a" => "orange", "b" => "banana", "c" => "apple");

foreach($fruits as $cls => $vls)
{
  $fruits[$cls] = "fruit: ".$vls;
}

Results: 

Array
(
    [d] => fruit: lemon
    [a] => fruit: orange
    [b] => fruit: banana
    [c] => fruit: apple
)

down

fantomx1 at gmail dot com ¶

8 years ago


Since array_walk cannot modify / change / reindex keys as already mentioned, i provide this small wrapping function which accomplishes passing array reference and index using closures , "use" keyword.

function indexArrayByElement($array, $element)
{
    $arrayReindexed = [];
    array_walk(
        $array,
        function ($item, $key) use (&$arrayReindexed, $element) {
            $arrayReindexed[$item[$element]] = $item;
        }
    );
    return $arrayReindexed;
}

down

alex_stanhope at hotmail dot com ¶

13 years ago


I wanted to walk an array and reverse map it into a second array.  I decided to use array_walk because it should be faster than a reset,next loop or foreach(x as &$y) loop.



<?php

$output = array();

array_walk($input, 'gmapmark_reverse', $output);



function gmapmark_reverse(&$item, $index, &$target) {

    $target[$item['form_key']] = $index;

}

?>



In my debugger I can see that $target is progressively updated, but when array_walk returns, $output is empty.  If however I use a (deprecated) call-by-reference:



<?php

array_walk($input, 'gmapmark_reverse', &$output);

?>



$output is returned correctly.  Unfortunately there's not an easy way to suppress the warnings:



<?php

@array_walk($input, 'gmapmark_reverse', &$output);

?>



doesn't silence them.  I've designed a workaround using a static array:



<?php

$reverse = array();

array_walk($input, 'gmapmark_reverse');

// call function one last time to get target array out, because parameters don't work

$reverse = gmapmark_reverse($reverse);



function gmapmark_reverse(&$item, $index = 0) {

  static $target;

  if (!$target) {

    $target = array();

  }

  if (isset($item['form_key'])) {

    $target[$item['form_key']] = $index;

  }

  return($target);

}

?>

down

brian at access9 dot net ¶

11 years ago


array_walk does not work on SplFixedArray objects:
<?php
$array = new SplFixedArray(2);
$array[0] = 'test_1';
$array[1] = 'test_2';

array_walk($array, function(&$val){
    $val .= '__';
    return $val;
});
foreach ($array as $a) {
    echo "$a\n";
}
?>

result is:
test_1
test_2

down

zlobnygrif at gmail dot com ¶

11 years ago


Some speed tests

<?php
// Test results
$array1 = test('array_walk');
$array2 = test('array_walk_list_each');
$array3 = test('array_walk_foreach1');
$array4 = test('array_walk_foreach2');

// Check arrays for equal
var_dump($array1 == $array2, $array1 == $array3, $array1 == $array4);

// Test function 1
function array_walk_list_each(&$array, $function, $userData = null) {
    while ( list($key, $value) = each($array) )
        $function($array[$key], $key, $userData);
}

// Test function 2
function array_walk_foreach1(&$array, $function, $userData = null) {
    foreach ($array as $key => &$value )
        $function($value, $key, $userData);
}

// Test function 3
function array_walk_foreach2(&$array, $function, $userData = null) {
    foreach ($array as $key => $value )
        $function($array[$key], $key, $userData);
}

function some_function(&$value, $key, $userData) {
    $value = "$key => $userData";
}

function test($function, $count = 10000, $arrayElements = 1000) {
    echo $function, ' ... ';
    $array = array_fill(0, $arrayElements, "some text value");
    
    $timer = microtime(true);
    for( $i = 0; ++$i < $count; )
        $function($array, 'some_function', 'some user data');
    printf("%.3f sec\n", microtime(true) - $timer);
    
    return $array;
}
?>

Output (PHP 5.4.9-4ubuntu2.2 (cli) (built: Jul 15 2013 18:24:39))
=========================
array_walk ... 13.572 sec
array_walk_list_each ... 0.027 sec
array_walk_foreach1 ... 15.356 sec
array_walk_foreach2 ... 17.416 sec
bool(true)
bool(true)
bool(true)

Output (PHP 5.5.0 (cli) (built: Jul 16 2013 17:59:42) - same server)
=========================
array_walk ... 4.776 sec
array_walk_list_each ... 0.006 sec
array_walk_foreach1 ... 4.482 sec
array_walk_foreach2 ... 5.166 sec
bool(true)
bool(true)
bool(true)

PHP 5.5 array_walk looks pretty good but list each is more and more quickly...

down

matthew at codenaked dot org ¶

14 years ago


Using lambdas you can create a handy zip function to zip together the keys and values of an array. I extended it to allow you to pass in the "glue" string as the optional userdata parameter. The following example is used to zip an array of email headers:



<?php



/**

 * Zip together the keys and values of an array using the provided glue

 * 

 * The values of the array are replaced with the new computed value

 * 

 * @param array $data

 * @param string $glue

 */

function zip(&$data, $glue=': ')

{

    if(!is_array($data)) {

        throw new InvalidArgumentException('First parameter must be an array');

    }



    array_walk($data, function(&$value, $key, $joinUsing) {

        $value = $key . $joinUsing . $value;

    }, $glue);

}



$myName = 'Matthew Purdon';

$myEmail = 'matthew@example.com';

$from = "$myName <$myEmail>";



$headers['From'] = $from;

$headers['Reply-To'] = $from;

$headers['Return-path'] = "<$myEmail>";

$headers['X-Mailer'] = "PHP" . phpversion() . "";

$headers['Content-Type'] = 'text/plain; charset="UTF-8"';



zip($headers);



$headers = implode("\n", $headers);

$headers .= "\n";



echo $headers;



/*

From: Matthew Purdon <matthew@example.com>

Reply-To: Matthew Purdon <matthew@example.com>

Return-path: <matthew@example.com>

X-Mailer: PHP5.3.2

Content-Type: text/plain; charset="UTF-8"

*/

?>

down

op_adept at yahoo dot co dot uk ¶

13 years ago


Prefix array values with keys and retrieve as a glued string, the original array remains unchanged. I used this to create some SQL queries from arrays.

<?php

function array_implode_prefix($outer_glue, $arr, $inner_glue, $prefix=false){
    array_walk( $arr , "prefix", array($inner_glue, $prefix) );
    return implode($outer_glue, $arr);
}

function prefix(&$value, $key, array $additional){
    $inner_glue = $additional[0];
    $prefix = isset($additional[1])? $additional[1] : false;
    if($prefix === false) $prefix = $key;

    $value = $prefix.$inner_glue.$value;
}

//Example 1:
$order_by = array("3"=>"ASC", "2"=>"DESC", "7"=>"ASC");
echo array_implode_prefix(",", $order_by, " ");
//Output: 3 ASC,2 DESC,7 ASC

//Example 2:
$columns = array("product_id", "category_id", "name", "description");
$table = "product";

echo array_implode_prefix(", ", $columns, ".", $table);
//Output:product.product_id, product.category_id, product.name, product.description 

//Example 3 (function prefix) won't really be used on its own
$pre= "vacation";
$value = "lalaland";
prefix($value, $pre, array("."));
echo $value;

//Output: vacation.lalaland

?>

down

jab_creations_-at_-yahoo_-dot-_com ¶

15 years ago


Unfortunately I spent a lot of time trying to permanently apply the effects of a function to an array using the array_walk function when instead array_map was what I wanted. Here is a very simple though effective example for those who may be getting overly frustrated with this function...

<?php
$fruits = array("Lemony & Fresh","Orange Twist","Apple Juice");

print_r($fruits);
echo '<br />';

function name_base($key)
{
 $name2 = str_replace(" ", "_", $key);
 $name3 = str_replace("&", "and", $name2);
 $name4 = strtolower($name3);
 echo $name4.'<br />';
 return $name4;
}
echo '<br />';

$test = array_map('name_base', $fruits);
$fruits_fixed = $test;
echo '<br />';
print_r($fruits_fixed);
?>

down

http://alex.moutonking.com/wordpress ¶

13 years ago


For completeness one has to mention the possibility of using this function with PHP 5.3 closures:



<?php

$names = array("D\'Artagnan", "Aramis", "Portos");

array_walk($names, function(&$n) {

  $n = stripslashes($n);

});

?>



The trap with array_walk being it doesn't return the array, instead it's modified by reference.

down

arekandrei at yandex dot ru ¶

14 years ago


You can use lambda function as a second parameter:

<?php
array_walk($myArray, function(&$value, $key){
    // if you want to change array values then "&" before the $value is mandatory.
});
?>

Example (multiply positive values by two):

<?php
$myArray = array(1, 2, 3, 4, 5);

array_walk($myArray, function(&$value, $index){
    if ($value > 0) $value *= 2;
});
?>

down

manuscle at gmail dot com ¶

12 years ago


example with closures, checking and deleting value in array:

<?php
$array = array('foo' => 'bar', 'baz' => 'bat');

array_walk($array, function($val,$key) use(&$array){ 
    if ($val == 'bar') { 
        unset($array[$key]);
    }
});

var_dump($array);

down

@jfredys ¶

13 years ago


I was looking for trimming all the elements in an array, I found this as the simplest solution:



<?php

array_walk($ids, create_function('&$val', '$val = trim($val);'));

?>

down

diyism ¶

16 years ago


When i pass the third parameter by reference in php5.2.5,
happened this: Warning: Call-time pass-by-reference has been deprecated - argument passed by value...

And to set allow_call_time_pass_reference to true in php.ini won't work, according to http://bugs.php.net/bug.php?id=19699   thus to work around:

<?php
array_walk($arrChnOut, create_function('&$v, $k, $arr_rtn', 'if ($k{0}!="_") {$arr_rtn[0]["_".$v[\'ID\']]=$v; unset($arr_rtn[0][$k]);}'), array(&$arrChnOut)); 
?>

down

theking2(at)king.ma ¶

10 months ago


This function can be used to add the values in one array to another:

<?php
echo '<pre>';
// example code
$a = [ 1, 2, 3, 4, 5, 6];
$c = [10,20,30,40,50,60];

array_walk($a,
  function(&$item, $key, $y) { $item += $y[$key];},
  $c
);

print_r($a);

// result

Array
(
    [0] => 11
    [1] => 22
    [2] => 33
    [3] => 44
    [4] => 55
    [5] => 66
)

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-1

christopher at crmldnrs dot com ¶

2 years ago


public function big_endian_array_walk(array $array, $callback) {
      end($array);
      for($i=sizeof($array);$i>0;$i--) {
        $key = key($array);
        $value = array_pop($array);
        if(preg_match('/^[a-zA-Z_\x80-\xff][a-zA-Z0-9_\x80-\xff]*$/', $value)) {
          call_user_func_array($callback, [$value, $key]);
        }
      }
    }

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-1

christopher at crmldnrs dot com ¶

2 years ago


public function big_endian_array_walk(array $array, $callback) {
      end($array);
      for($i=sizeof($array);$i>0;$i--) {
        $key = key($array);
        $value = array_pop($array);
        if(preg_match('/^[a-zA-Z_\x80-\xff][a-zA-Z0-9_\x80-\xff]*$/', $value)) {
          call_user_func_array($callback, [$value, $key]);
        }
      }
    }

I just wanted to walk from the end to the beginning.

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-1

vrrivaro at YESIUSEGMAIL dot gmail dot SO dot com ¶

7 years ago


The output of the example is only correct if viewed through a web browser. If you pass it through to PHP-CLI, you will get to see the additional HTML line breaks, however.

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-1

emre ¶

3 years ago


You can change the key or value with array_walk if you use the temporal returned array in global inside the function. For example:

$array = ['a'=>10, 'b'=>20];
$sequence = array ();

$newArray = array_values(array_walk($array, 'fn'));

function fn(&$val,$key){

global $sequence;

$sequence [] = $val;

}

No need to concern about the place of the internal pointer for the baby array. You have now rewinded, 0 based new array, string key one instead.

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-1

mystral77 at gmail dot com ¶

4 years ago


Hello,

If you want to add values with same key from two arrays :

<?php
function add(&$item,$key,$search) {
    $item += (is_array($search))?((isset($search[$key]))?$search[$key]:0):0;
}

$a = ["orange" => 2, "banana" => 3, "apple" => 1];
$b = ["orange" => 1, "apple" => 4];

array_walk($c,"add",$b);

echo "<pre>".print_r($c,true)."</pre>";
?>

This will output:

"orange" => 3,
"banana" => 3,
"apple" => 5

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-2

espertalhao04 at hotmail dot com ¶

11 years ago


here is a simple and yet easy to use implementation of this function.
the 'original' function has the problem that you can't unset a value.
with my function, YOU CAN!

<?php
function array_walk_protected(&$a,$s,$p=null)
{
    if(!function_exists($s)||!is_array($a))
    {
        return false;
    }
    
    foreach($a as $k=>$v)
    {
        if(call_user_func_array($s,array(&$a[$k],$k,$p))===false)
        {
            unset($a[$k]);
        }
    }
}

function get_name(&$e,$i,$p)
{
    echo "$i: $e<br>";
    return false;
}

$m=array('d'=>'33','Y'=>55);

array_walk_protected($m,'get_name');

var_dump($m); //returns array(0) { }
?>

i called it array_walk_protected because it is protected against the unexpected behavior of unsetting the value with the original function.

to delete an element, simply return false!!!
nothing else is needed!
unsetting $e, under your created function, will keep the same array as-is, with no changes!

by the way, the function returns false if $a is not array or $s is not a string!

limitations: it only can run user defined functions.
i hope you like it!

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-3

gold[at]evolved.net.nz ¶

11 years ago


For all those people trying to shoe-horn trim() into array_walk() and have found all these tricks to work around the issue with array_walk() passing 2 parameters to the callback...

Check out array_map().

http://php.net/array_map

It's all sorts of win.

For the record. I'm one of these people and after 15 years of php development I'm pleased to say that there's still things I'm learning. :)  I just found out about array_map() myself...

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-2

el_porno at web dot de ¶

19 years ago


You want to get rid of the whitespaces users add in your form fields...?
Simply use...:

class SomeVeryImportantClass
{
...
    public function mungeFormData(&$data)
    {
        array_walk($data, array($this, 'munge'));
    }

    private function munge(&$value, &$key)
    {
        if(is_array($value))
        {
            $this->mungeFormData($value);
        }
        else
        {
            $value = trim($value);
        }
    }
...
}

so...
$obj = new SomeVeryImportantClass;
$obj->mungeFormData($_POST);
___
eNc

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-4

jerk at yoosic dot de ¶

17 years ago


if you want to modify every value of an multidimensional array use this function used here:

<?php

$array = array (1=>1, 2=> 2, 3 => array(1=>11, 2=>12, 3=>13));
$text = "test";

function modarr(&$array, $text) {
        foreach ($array as $key => $arr) {
                if(is_array($arr)) $res[$key] = modarr(&$arr,$text);
                // modification function here
                else $res[$key] = $arr.$text;
                }
        return $res;
}

$erg = modarr($array, $text);

print_r($erg);  

?>

result will be_

<?php
Array ( [1] => 1test [2] => 2test [3] => Array ( [1] => 11test [2] => 12test [3] => 13test ) )
?>

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-3

peterzuzek AT gmail DOT com ¶

16 years ago


I had some problems using this function - it didn't want to apply PHP-defined functions. So I decided to write my own - here it is. I had to use some generic-programming skills, didn't really checked the speed (I think it could be slow)... I believe it could be much better, but I don't know, how - well, I guess multiple array support and recursion would be nice. So?

Prototype:
bool arrayWalk(array &$arry, callback $callback, mixed $params=false)

<?php

    function arrayWalk(&$arry, $callback, $params=false) {
        $P=array(""); // parameters
        $a=""; // arguement string :)

        if($params !== false) { // add parameters
            if(is_array($params)) { // multiple additional parameters
                foreach($params as $par)
                    { $P[]=$par; }
            }
            else // just one additional
                { $P[]=$params; }
        }

        for( // create the arguement string
            $i=0; isset($P[$i]); ++$i
        )
            { $a.='$'.chr($i + 97).', '; } // random argument names

        $a=substr($a, 0, -2); // to get rid of the last comma and two spaces

        $func=create_function($a, 'return '.$callback.'('.$a.');'); // the generic function

        if(is_callable($func)) {
            for( // cycle through array
                $i=0; isset($arry[$i]); ++$i
            ) {
                $P[0]=$arry[$i]; // first element must be the first argument - array value
                $arry[$i] = call_user_func_array($func, $P); // assign the new value obtained by the generic function
            }
        }
        else
            { return false; } // failure - function not callable

        return true; // success!
    } // arrayWalk()

?>

One big problem I've noticed so far - for example, if you wanted to use str_replace on the array, you'd fail - simply because of the arguement order of str_replace, where the string modified is the third arguement, not the first as arrayWalk requires.

So, still some work left...

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-4

Enlightened One ¶

19 years ago


Beware that "array ($this, method)" construct. If you're wanting to alter members of the "$this" object inside "method" you should construct the callback like this:

  $callback[] = &$this;
  $callback[] = method;
  array_walk ($input, $callback);

Creating your callback using the array() method as suggested by "appletalk" results in a copy of $this being passed to method, not the original object, therefor any changes made to the object by method will be lost when array_walk() returns. While you could construct the callback with "array(&$this, method)", I believe this relies on the deprecated runtime pass-by-reference mechanism which may be removed in future releases of PHP. Better to not create a dependence on that feature now than having to track it down and fix it in the future.

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-5

tufanbarisyildirim at gmail dot com ¶

13 years ago


Filter an array by using key.

<?php
    $product_1 = 'test';
    $product_2 = 'test 2';

    function array_key_filter($array,$callback = 'trim')
    {   
        $filtered = array();
        array_walk($array,function ($degeri,$degisken_adi) use (&$filtered,$callback)
        {   
            if($callback($degisken_adi))
            {
                $filtered[$degisken_adi] =  $degeri;
            }   
        });

        return $filtered;         
    }

    #using

    $degiskenler = array_key_filter(get_defined_vars(),function($key) 
    { 
        return strpos($key,'product_') === 0; 
    });

    print_r($degiskenler);
?>
output:

Array
(
    [product_1] => test
    [product_2] => test 2
)

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