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array> <array_walk_recursive
Last updated: Fri, 18 May 2012

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array_walk

(PHP 4, PHP 5)

array_walk — Wendet eine Benutzerfunktion auf jedem Element eines Arrays an

Beschreibung

bool array_walk ( array &$array , callback $funcname [, mixed $userdata ] )

Wendet die mittels funcname angegebene Benutzerfunktion auf jedes Element von array an.

array_walk() ist nicht von dem internen Arrayzeiger von array betroffen. array_walk() geht ungeachtet der Zeigerposition das gesamte Array durch.

Parameter-Liste

array

Das Eingabe-Array.

funcname

Typischerweise akzeptiert funcname zwei Parameter. Der Wert von array wird als erster übergeben, und der Schlüssel/Index als zweiter.

Hinweis:

Wenn funcname direkt mit den Werten des Arrays arbeiten soll, spezifizieren Sie den ersten Parameter von funcname als Referenz. Dann werden alle Änderungen an diesen Elementen direkt in dem originalen Array durchgeführt.

Hinweis:

Viele interne Funktionen (wie z.B. strtolower()) erzeugen eine Warnung, wenn mehr als die erwartete Anzahl von Parametern übergeben wird; sie sind auch nicht direkt nutzbar als funcname.

Nur die Werte von array können geändert werden. Die Struktur des Arrays kann nicht geändert werden, d.h. dass der Programmierer keine Elemente hinzufügen oder löschen kann und dass die Reihenfolge der Elemente nicht geändert werden kann. Falls die Callback-Funktion diese Anforderung nicht beachtet, ist der Verhalten dieser Funktion nicht definiert und auch nicht vorhersagbar.

userdata

Wenn der optionale Parameter userdata angegeben ist, wird er als dritter Parameter dem Callback funcname übergeben.

Rückgabewerte

Gibt bei Erfolg TRUE zurück. Im Fehlerfall wird FALSE zurückgegeben.

Fehler/Exceptions

Sollte die Funktion funcname mehr als die ihr übergebenen Parameter benötigen, wird bei jedem Aufruf von funcname durch array_walk() eine Fehlermeldung der Stufe E_WARNING generiert. Diese Warnmeldungen können unterdrückt werden, indem man dem Funktionsaufruf von array_walk() den Operator @ voranstellt, oder error_reporting() verwendet.

Beispiele

Beispiel #1 array_walk()-Beispiel

<?php
$fruits = array("d" => "Zitrone", "a" => "Orange", "b" => "Banane", "c" => "Apfel");

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

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

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

array_walk($fruits, 'test_alter', 'Frucht');
echo "... und nachher:\n";

array_walk($fruits, 'test_print');
?>

Das oben gezeigte Beispiel erzeugt folgende Ausgabe:

Vorher ...:
d. Zitrone
a. Orange
b. Banane
c. Apfel
... und nachher:
d. Frucht: Zitrone
a. Frucht: Orange
b. Frucht: Banane
c. Frucht: Apfel

Siehe auch

  • array_walk_recursive() - Wendet eine Benutzerfunktion rekursiv auf jedes Element eines Arrays an
  • iterator_apply() - Call a function for every element in an iterator
  • create_function() - Erzeugen einer anonymen / temporären (Lambda-Stil) Funktion
  • list() - Weist Variablen zu, als wären sie ein Array
  • each() - Liefert das aktuelle Paar (Schlüssel und Wert) eines Arrays und rückt den Arrayzeiger vor
  • call_user_func_array() - Call a callback with an array of parameters
  • array_map() - Wendet eine Callback-Funktion auf die Elemente von Arrays an
  • Informationen über den Callback-Typ
  • foreach



add a note add a note User Contributed Notes
array_walk
Jon Langevin >>intel352 : AT : gmail.com
19-Jan-2007 09:15
In response to "Andrzej Martynowicz at gmail dot com", regarding the use of array_walk with the optional 3rd parameter being modified by reference:

while your solution works, yet another option is to call array_walk like so:

<?php
array_walk($array1, 'userfunction', &$array2byreference);

function userfunction(&$array1value, $key, $array2){
     // process $array1value and $array2, $array2 will retain the values
}
?>
hioctiane at hioctiane dot de
22-Dec-2006 11:00
<?php
/*Thanks to Jerk, thats what I need all the time.
I have a little Upgrade to your code.
Now the values of your $array will be handled by a consign method from a consign object(optional, otherwise taking this operator).*/

class user_function {

 function user_function() {
 }

 /**
  *
  * handle all values from multidimensional array by $function from $object
  *
  */
 function walk_multi_array(&$array, $method, $object=NULL) {
    //when argument object is given
    if (is_object($object)) {
        //check if it is object
        if (!is_object($object))
            return false;
        //check if object has method
        if (!array_search(strtolower($method), get_class_methods(get_class($object))))
            return false;
    }
    //no argument object is given
    else {
        //check if this class has method
        if (!array_search(strtolower($method), get_class_methods(get_class($this))))
            return false;
    }
    foreach ($array as $key => $value) {
        //$value is array
        if(is_array($value))
            //recursiv call of walk_multi_array
            $result[$key] = $this->walk_multi_array(&$value, $method, $object);
        //$value is value
        else {
            if (is_object($object))
                $result[$key] = $object->$method($value);
            else
                $result[$key] = $this->$method($value);
        }
    }
    return $result;
 }
}

class  test_class {

 function test_class() {
 }

 function strtoup($value) {
    return strtoupper($value);
 }
}

$test_class = new test_class;
$user_function = new user_function;
$array = array    (
    1 => "testFall1",
    2 => array (
        21 => "tesTfaLL21",
        22 => array (
            221 => "TESTFALL221",
            222 => "testfall222"
                )
           ),
    3 => "testfall3"       
        );
echo "<pre>";
print_r($user_function->walk_multi_array($array, 'strtoup', $test_class));
echo "</pre>";
?>

Output:

Array
(
    [1] => TESTFALL1
    [2] => Array
        (
            [21] => TESTFALL21
            [22] => Array
                (
                    [221] => TESTFALL221
                    [222] => TESTFALL222
                )

        )

    [3] => TESTFALL3
)
jerk at yoosic dot de
21-Dec-2006 05:05
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 ) )
?>
nihaopaul at nihaopaul dot com
06-May-2006 12:59
no sure if this should go under array-walk but it does what i need, it searches a multidimensionial array by using an array to walk it, it either returns a value or an array.

function walker($walk, $array) {
    if (count($walk) >0) {
        foreach($array as $key => $value) {
            if ($key == $walk[0]) {
                if (is_array($value)) {
                    unset($walk[0]);
                    return walker(array_values($walk), $value);
                } else {
                    if (isset($value)) {
                        if (count($walk) == 1) {
                            return $value;
                        } else {
                            return 0;
                        }
                    } else {
                        return 0;
                    }
                }
            }
        }
        return 0;
    } else {
        return $array;
    }
}
ludvig dot ericson at gmail dot com
21-Nov-2005 03:09
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 $x would be much faster ;-) just a sample.
ibolmo
18-Nov-2005 04:53
If anyone is interested to implement the array_walk functionality to a string. I've made this handy function. Note that this can be easily extended for any type of purpose. I've used this to convert from a string of bytes to a hex string then back from hex to a byte string.
<?php
function string_walk($string,$funcname)
{
    for($i=0;$i<strlen($string);$i++) {
        call_user_func($funcname,$string{$i});
    }
}

function yourFunc($val)
{
    echo $val.' ';
}

string_walk('interesting','yourFunc');
//ouput: i n t e r e s t i n g
?>
thomas dot hebinck at digionline dot de
31-Oct-2005 03:07
This is a short way to concatenate a string to each element of an array:

$arr=array(1,2,3,4,5,6,7,8,9,0);
$str=' test'; // must not include ' or " ...

array_walk($arr,create_function('&$elem','$elem .= "' . $str . '";'));

var_export($arr);

The output is:
array ( 0 => '1 test', 1 => '2 test', 2 => '3 test', 3 => '4 test', 4 => '5 test', 5 => '6 test', 6 => '7 test', 7 => '8 test', 8 => '9 test', 9 => '0 test', )
Andrzej Martynowicz at gmail dot com
19-Sep-2005 03:03
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:

<?
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..

<?
$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.
webmaster at tmproductionz dot com
18-Jul-2005 09:54
to the note right before this one.  that will only trim leading and trailing white space. if you want to trim white space inside the string (ie 'hello     world' to 'hello world') you should use this:

$val = preg_replace ( "/\s\s+/" , " " , $val ) ;

this will also trim leading and trailing white space.
el_porno at web dot de
27-May-2005 12:03
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
caliban at darklock dot com
23-May-2005 07:33
> I believe this relies on the deprecated runtime
> pass-by-reference mechanism

The array() keyword is a language construct, not a function, so I don't think this is applicable.
Enlightened One
08-Apr-2005 08:17
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.
Hayley Watson
17-Jan-2005 03:27
As well as being able to pass the array the callback will be working on by reference, one can pass the optional userdata parameters by reference also:
<?php

function surprise($x,$key,$xs)
{
    //$key is unused here.
    $x.='!';
    array_push($xs,$x);
}

$array1 = array('this','that','the other');
$array2 = array();

array_walk($array1,'surprise',&$array2);

print_r($array1);
print_r($array2);
?>
Of course, that precise example would be better handled by array_map, but the principle is there.
appletalk at gmail dot com
23-Dec-2004 03:26
To use array_walk with a class simply do:
array_walk($input, array($this, method) );
memandeemail at gmail dot com
11-Nov-2004 02:24
If you are using array_walk on a class, dont will work

so ... try this on your own class:

class your_own_class {
    /**
    * @return void
    * @param array $input
    * @param string $funcname
    * @desc A little workaround, do the same thing.
    */
    function array_walk($input, $funcname) {
        foreach ($input as $key => $value) $this->$funcname($value, $key);
    }
}
05-Nov-2004 08:22
If array_walk_recursive() is not present and you want to apply htmlentities() on each array element you can use this:

function array_htmlentities(&$elem)
{
  if (!is_array($elem))
  {
    $elem=htmlentities($elem);
  }
  else
  {
    foreach ($elem as $key=>$value)
      $elem[$key]=array_htmlentities($value);
  }
  return $elem;
} // array_htmlentities()

If you want to output an array with print_r() and you have html in it this function is very helpful.
lgaga dot dont dot spam at muszaki dot info
16-Oct-2004 04:31
Behaviour like array_walk_recursive() can be achieved in php <=5 by a callback function to array_walk() similar to this:

function walkcallback(&$val,$key) {
    if (is_array($val)) array_walk($val,'walkcallback',$new);
    else {
        // do what you want with $val and $key recursively
    }
}
bisqwit at iki dot fi
04-Sep-2004 01:54
It's worth nothing that array_walk can not be used to change keys in the array.
The function may be defined as (&$value, $key) but not (&$value, &$key).
Even though PHP does not complain/warn, it does not modify the key.
paul at heliosville dot com
03-Sep-2004 09:13
one rather important note that was lost in the Great PHP Doc Note Purge of '04 is that you can call methods using array_walk(). Let's assume that we have a class named 'Search', in which there is a method called 'convertKeywords'. Here's how you would call that convertKeywords method from inside the class:

    array_walk($keywords, array($this, 'convertKeywords'));

Notice that, instead of giving a string as the second argument, you give an array with two items: the variable that holds the class (in this case, $this), and the method to call. Here's what it would look like if you were to call convertKeywords from an already-instantiated class:

    $search = new Search;
    array_walk($keywords, array($search, 'convertKeywords'));
Eierkoek
03-Sep-2004 03:46
normaly the $_GET array will add slashes to the array values. To remove all slashes in this array, i created the folowing code

  set_magic_quotes_runtime (0);
  function StripAllSlashes (&$ArrayGET, $Value)
  {
    if (is_array ($ArrayGET)) array_walk ($ArrayGET, "StripAllSlashes");
    else $ArrayGET = stripslashes ($ArrayGET);
  }
  if (isset ($_GET) && get_magic_quotes_gpc ()) array_walk ($_GET, "StripAllSlashes");

I hope this code was usefull,

Eierkoek
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array> <array_walk_recursive
Last updated: Fri, 18 May 2012