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foreach

(PHP 4, PHP 5, PHP 7)

foreach yapısı diziler üzerinde yineleme yapmayı kolaylaştırmaktadır. foreach yalnızca diziler ve nesneler için kullanılabilir; farklı veri türünde veya ilklendirilmemiş bir değişken ile kullanmak istediğinizde hata verir. İki sözdizimi mevcuttur:

foreach (dizi_ifadesi as $değer)
    deyim
foreach (dizi_ifadesi as $isim => $değer)
    deyim

İlk sözdizimi dizi_ifadesi ile belirtilen dizinin üzerinde döngü oluşturur. Her yinelemede, sırası gelen elemanın değeri $değer değişkenine atanır ve dizi göstericisi bir arttırılır (böylece bir sonraki yinelemede dizinin bir sonraki elemanına bakılması sağlanmış olur).

İkinci yöntem de aynı şeyi yapar, ek olarak her yinelemede sırası gelen elemanın anahtarı $isim değişkenine atanır.

PHP 5'den itibaren, nesneleri yinelemek mümkün olmuştur.

Bilginize:

foreach ilk çalışmaya başladığında, dizi göstericisi özdevinimli olarak ilk elemanı gösterecek biçimde sıfırlanır. Bu sebeple, foreach deyiminden önce reset() işlevini çalıştırmanıza gerek yoktur.

foreach dahili bir dizi göstericisi ile çalışması nedeniyle bunun döngü içinde değiştirilmesi beklenmedik sonuçlara yol açabilir.

$değer değişkeninin önüne & koyarak dizi elemanları üzerinde kolayca değişiklik yapılabilir. Böylece değer gönderimli hale gelir.

<?php
$dizi 
= array(1234);
foreach (
$dizi as &$değer) {
    
$değer $değer 2;
}
// $dizi artık array(2, 4, 6, 8) olmuştur
unset($değer); // son eleman da işlendiğine göre gönderimi kaldıralım
?>

$değer değişkeninin gönderimli hale getirilebilmesi, sadece yinelenen dizi gönderimli (örn, bir değişkene) olabiliyorsa mümkündür, yani aşağıdaki kod çalışmaz:

<?php
foreach (array(1234) as &$value) {
    
$value $value 2;
}
?>

Uyarı

$değer gönderim için kullanıldığından foreach döngüsünün sonunda son dizi elemanına gönderimli olarak kalır, bu bakımdan döngünün sonunda bu gönderimin unset() işlevi kullanılarak kaldırılması önerilir.

Bilginize:

foreach, hata iletilerinin '@' kullanılarak gözardı edilmesi özelliğini desteklemez.

Aşağıdaki iki döngünün aynı işi yaptığını farkedeceksiniz:

<?php
$dizi 
= array("bir""iki""üç");
reset($dizi);
while (list(, 
$değer) = each($dizi)) {
    echo 
"Değer: $değer<br />\n";
}

foreach (
$dizi as $değer) {
    echo 
"Değer: $değer<br />\n";
}
?>

Aşağıdakiler de işlevsel olarak aynıdır:

<?php
$dizi 
= array("bir""iki""üç");
reset($dizi);
while (list(
$isim$değer) = each($dizi)) {
    echo 
"Anahtar: $isim; Değer: $değer<br />\n";
}

foreach (
$dizi as $isim => $değer) {
    echo 
"Anahtar: $isim; Değer: $değer<br />\n";
}
?>

Değişik kullanımlara örnekler:

<?php
/* foreach örneği 1: yalnızca değer */

$a = array(12317);

foreach (
$a as $v) {
   echo 
"\$a değişkeninin şu anki değeri: $v.\n";
}

/* foreach örneği 2: değer (örnek olması için anahtar
 *  ile birlikte yazdırılmıştır) */

$a = array(12317);

$i 0/* yalnızca örnekleme için */

foreach ($a as $v) {
    echo 
"\$a[$i] => $v.\n";
    
$i++;
}

/* foreach örneği 3: anahtar ve değer */

$a = array(
    
"bir" => 1,
    
"iki" => 2,
    
"üç"  => 3,
    
"on yedi" => 17
);

foreach (
$a as $k => $v) {
    echo 
"\$a[$k] => $v.\n";
}

/* foreach örneği 4: çok boyutlu diziler */
$a = array();
$a[0][0] = "a";
$a[0][1] = "b";
$a[1][0] = "y";
$a[1][1] = "z";

foreach (
$a as $v1) {
    foreach (
$v1 as $v2) {
        echo 
"$v2\n";
    }
}

/* foreach örneği 5: devingen diziler */

foreach (array(12345) as $v) {
    echo 
"$v\n";
}
?>

İç içe dizilerin list() ile ayrıştırılması

(PHP 5 >= 5.5.0, PHP 7)

PHP 5.5 ile yeni bir yetenek eklendi. Dizi dizileri üzerinde döngü oluşturmak ve list() işlevini değer olarak kullanmak suretiyle içteki diziyi döngü değişkenlerine atayarak onu da açmak artık mümkündür.

Örneğin:

<?php
$dizi 
= [
    [
12],
    [
34],
];

foreach (
$dizi as list($a$b)) {
    
// $a içteki dizinin ilk elemanını,
    // $b ikinci elemanını içerecektir.
    
echo "A: $a; B: $b\n";
}
?>

Yukarıdaki örneğin çıktısı:

A: 1; B: 2
A: 3; B: 4

İçteki dizinin gerekmeyen elemanlarını list() içinde içermeyebilirsiniz:

<?php
$dizi 
= [
    [
12],
    [
34],
];

foreach (
$dizi as list($a)) {
    
// Burada artık $b yok.
    
echo "$a\n";
}
?>

Yukarıdaki örneğin çıktısı:

1
3

list() için yeterli sayıda dizi elemanı yoksa bir uyarı üretilir.:

<?php
$dizi 
= [
    [
12],
    [
34],
];

foreach (
$dizi as list($a$b$c)) {
    echo 
"A: $a; B: $b; C: $c\n";
}
?>

Yukarıdaki örneğin çıktısı:


Notice: Undefined offset: 2 in example.php on line 7
A: 1; B: 2; C:

Notice: Undefined offset: 2 in example.php on line 7
A: 3; B: 4; C:

add a note add a note

User Contributed Notes 22 notes

up
173
adam dot sindelar at gmail dot com
8 years ago
You can also use the alternative syntax for the foreach cycle:

<?php
foreach($array as $element):
 
#do something
endforeach;
?>

Just thought it worth mentioning.
up
93
php at darkain dot com
3 years ago
"Reference of a $value and the last array element remain even after the foreach loop. It is recommended to destroy it by unset()."

I cannot stress this point of the documentation enough! Here is a simple example of exactly why this must be done:

<?php
$arr1
= array("a" => 1, "b" => 2, "c" => 3);
$arr2 = array("x" => 4, "y" => 5, "z" => 6);

foreach (
$arr1 as $key => &$val) {}
foreach (
$arr2 as $key => $val) {}

var_dump($arr1);
var_dump($arr2);
?>

The output is:
array(3) { ["a"]=> int(1) ["b"]=> int(2) ["c"]=> &int(6) }
array(3) { ["x"]=> int(4) ["y"]=> int(5) ["z"]=> int(6) }

Notice how the last index in $arr1 is now the value from the last index in $arr2!
up
39
tedivm at tedivm dot com
8 years ago
foreach and the while/list/each methods are not completely identical, and there are occasions where one way is beneficial over the other.

<?php
$arr
= array(1,2,3,4,5,6,7,8,9);

foreach(
$arr as $key=>$value)
{
    unset(
$arr[$key + 1]);
    echo
$value . PHP_EOL;
}
?>
Output:
1 2 3 4 5 6 7 8 9

<?php
$arr
= array(1,2,3,4,5,6,7,8,9);

while (list(
$key, $value) = each($arr))
{
    unset(
$arr[$key + 1]);
    echo
$value . PHP_EOL;
}
?>
Output:
1 3 5 7 9


[EDIT BY danbrown AT php DOT net: Contains a typofix by (scissor AT phplabs DOT pl) on 30-JAN-2009.]
up
20
Alastair Hole
2 years ago
What happened to this note:
"Unless the array is referenced, foreach operates on a copy of the specified array and not the array itself. foreach has some side effects on the array pointer. Don't rely on the array pointer during or after the foreach without resetting it."

Is this no longer the case?
It seems only to remain in the Serbian documentation: http://php.net/manual/sr/control-structures.foreach.php
up
18
Oleg englishman at bigmir dot net
6 years ago
For those who'd like to traverse an array including just added elements (within this very foreach), here's a workaround:

<?php
$values
= array(1 => 'a', 2 => 'b', 3 => 'c');
while (list(
$key, $value) = each($values)) {
    echo
"$key => $value \r\n";
    if (
$key == 3) {
       
$values[4] = 'd';
    }
    if (
$key == 4) {
       
$values[5] = 'e';
    }
}
?>

the code above will output:

1 => a
2 => b
3 => c
4 => d
5 => e
up
12
Fred
2 years ago
If you want to use the list for multidimension arrays, you can nest several lists:

<?php
$array
= [
    [
1, 2, array(3, 4)],
    [
3, 4, array(5, 6)],
];

foreach (
$array as list($a, $b, list($c, $d))) {
    echo
"A: $a; B: $b; C: $c; D: $d;<br>";
};
?>

Will output:
A: 1; B: 2; C: 3; D: 4;
A: 3; B: 4; C: 5; D: 6;

And:

<?php
$array
= [
    [
1, 2, array(3, array(4, 5))],
    [
3, 4, array(5, array(6, 7))],
];

foreach (
$array as list($a, $b, list($c, list($d, $e)))) {
    echo
"A: $a; B: $b; C: $c; D: $d; E: $e;<br>";
};
Will output:
A: 1; B: 2; C: 3; D: 4; E: 5;
A: 3; B: 4; C: 5; D: 6; E: 7;
?>
up
1
mustaroad
3 months ago
in foreach if you want to iterate through a specific column in a nested arrays for example:

$arr = array(
     [1, 2, 3,   4],
     [14, 6, 7,  6],
     [10, 2 ,3 , 2],
);

when we want to iterate on the third column we can use:

foreach( $arr as list( , , $a)) {
    echo "$a\n";
}

this will print:
3
7
3
up
4
sebastian dot goendoer at NOSPAM dot telekom dot de
1 year ago
String keys of associative arrays, for which is_numeric() is true and which can be type-juggled to an int will be cast to an int! If the key is on the other hand a string that can be type-juggled into a float, it will stay a string. (Observed on PHP 7.0.0RC8)

<?php
$arr
= array();
$arr[0] = "zero";            // will stay an int
$arr["1"] = "one";            // will be cast to an int !
$arr["two"] = "2";            // will stay a string
$arr["3.5"] = "threeandahalf";    // will stay a string

foreach($arr as $key => $value) {
   
var_dump($key);
}
?>

The output will be

int(0)
int(1)
string(3) "two"
string(3) "3.5"
up
4
Anonymous
2 years ago
modifying array while foreach'ing it(yeah, such slime code;-)
if elements were added on last iteration or into array with 1 element, then added elements wont be iterated as foreach checks for pointer before iteration cycle
so it just quit and added elements wont be treated
up
8
dtowell
4 years ago
References created by foreach hang around past their best-used-by date. For example, the following:

<?php
$a
= array('abe','ben','cam');
foreach (
$a as $k=>&$n)
   
$n = strtoupper($n);
foreach (
$a as $k=>$n) // notice NO reference here!
   
echo "$n\n";
print_r($a);
?>

will result in:

ABE
BEN
BEN
Array
(
    [0] => ABE
    [1] => BEN
    [2] => BEN
)
up
0
John
3 hours ago
WARNING: Looping through "values by reference" for "extra performance" is an old myth. It's actually WORSE!

<?php

function one($arr) {
    foreach(
$arr as $val) { // Normal Variable
       
echo $val;
    }
}

function
two($arr) {
    foreach(
$arr as &$val) { // Reference To Value
       
echo $val;
    }
}

$a = array( 'a', 'b', 'c' );
one($a);
two($a);

?>

Which do you think is faster?

Lots of people think the answer is two() because it uses "reference to value, which it doesn't have to copy each value when it loops".

Well, that's totally wrong!

Here's what actually happens:

* one():

- This function takes an array as argument ($arr).
- The array function argument itself isn't passed by reference, so the function knows it isn't allowed to modify the original at all.
- Then the foreach loop happens. The array itself wasn't passed by reference to the function, so PHP knows that it isn't allowed to modify the outside array, so it therefore makes a copy of the array's internal iteration offset state (that's just a simple number which says which item you are currently at during things like foreach()), which costs almost no performance or memory at all since it's just a small number.
- Next, it uses that copied iteration offset to loop through all key/value pairs of the array (ie 0th key, 1st key, 2nd key, etc...). And the value at the current offset (a PHP "zval") is assigned to a variable called $val.
- Does $val make a COPY of the value? That's what MANY people think. But the answer is NO. It DOESN'T. It re-uses the existing value in memory. With zero performance cost. It's called "copy-on-write" and means that PHP doesn't make any copies unless you try to MODIFY the value.
- If you try to MODIFY $val, THEN it will allocate a NEW zval in memory and store $val there instead (but it still won't modify the original array, so you can rest assured).

Alright, so what's the second version doing? The beloved "iterate values by reference"?

* two():

- This function takes an array as argument ($arr).
- The array function argument itself isn't passed by reference, so the function knows it isn't allowed to modify the original at all.
- Then the foreach loop happens. The array itself wasn't passed by reference to the function, so PHP knows that it isn't allowed to modify the outside array.
- But it also sees that you want to look at all VALUES by reference (&$val), so PHP says "Uh oh, this is dangerous. If we just give them references to the original array's values, and they assign some new value to their reference, they would destroy the original array which they aren't allowed to touch!".
- So PHP makes a FULL COPY of the ENTIRE array and ALL VALUES before it starts iterating. YIKES!

Therefore: STOP using the old, mythological "&$val" iteration method! It's almost always BAD! With worse performance, and risks of bugs and quirks as is demonstrated in the manual.

You can always manually write array assignments explicitly, without references, like this:

<?php

$a
= array(1, 2, 3);
foreach(
$a as $key => $val) {
  
$a[$key] = $val * 10;
}
// $a is now [10, 20, 30]

?>

The main lesson is this: DON'T blindly iterate through values by reference! Telling PHP that you want direct references will force PHP to need to copy the WHOLE array to protect its original values! So instead, just loop normally and trust the fact that PHP *is* actually smart enough to never copy your original array's values! PHP uses "copy-on-write", which means that attempting to assign something new to $val is the ONLY thing that causes a copying, and only of that SINGLE element! :-) But you never do that anyway, when iterating without reference. If you ever want to modify something, you use the "$a[$key] = 123;" method of updating the value.

Enjoy and good luck with your code! :-)
up
0
Delian Krustev
3 years ago
I want to add some inline comments to dtowell's piece of code about the iteration by reference:

<?php

$a
= array('abe','ben','cam');

foreach (
$a as $k=>&$n)
   
$n = strtoupper($n);

# At the end of this cycle the variable $n refers to the same memory as $a[2]
# So when the second "foreach" assigns a value to $n :

foreach ($a as $k=>$n) // notice NO reference here!
   
echo "$n\n";

# it is also modifying $a[2] .
# So on the three repetitions of the second "foreach" the array will look like:
# 1. ('abe','ben','abe') - assigned the value of the first element to the last element
# 2. ('abe','ben','ben') - assigned the value of the second element to the last element
# 3. ('abe','ben','ben') - assigned the value of the third element to itself

print_r($a);
?>
up
-5
nobody at nobody dot com
5 years ago
<?php
$d3
= array('a'=>array('b'=>'c'));
foreach(
$d3['a'] as &$v4){}
foreach(
$d3 as $v4){}
var_dump($d3);
?>
will get something look like this:
array(1) {
  ["a"]=>
  array(1) {
    ["b"]=>
    &array(1) {
      ["b"]=>
      *RECURSION*
    }
  }
}
then you try to walk some data with this array.
the script run out of memory and connect reset by peer

the document says:
Warning
Reference of a $value and the last array element remain even after the foreach loop. It is recommended to destroy it by unset().

so what I learn is that NEVER ignore """Warning""" in document....
up
-6
billardmchl at aol dot com
5 years ago
This function find well the words, add well adds a () around short words, but the
array at the end of th function is the same as at the beginning.

<?php
function isole_mots($chaine)
{
   
$chaine = "le petit chat est fou";
   
$mots = preg_split('/[!,-.;?:()[ ]/', $chaine, -1, PREG_SPLIT_NO_EMPTY);
    foreach (
$mots as $mot)
    {
        if (
strlen($mot) <= 3)
           
$mot = "(".$mot.")";
    print
" inside foreach $mot <br>";
    }
print
"after foreach array mots";   
   
print_r($mots);
    die();
    return
$mots;
}
?>

inside foreach (le)
inside foreach petit
inside foreach chat
inside foreach (est)
inside foreach (fou)
after foreach array motsArray ( [0] => le [1] => petit [2] => chat [3] => est [4] => fou )
up
-6
nehuen
2 years ago
foreach by reference internally deleted and created a new reference in each iteration, so it is not possible to directly use this value as a variable parameter values​​, look at the following example where the problem is observed and a possible solution:

<?php
class test
{
    private
$a = false;
    private
$r = null;
    public function
show(&$v)
    {
        if(!
$this->a)
        {
           
$this->a = true;
           
$this->r = &$v;
        }
       
var_dump($this->r);
    }
    public function
reset()
    {
       
$this->a = false;   
    }
}

$t = new test();

$a = array(array(1,2),array(3,4),array(5,6));
foreach(
$a as &$p)
   
$t->show($p);
   
/* Output obtain:
    array (size=2)
      0 => int 1
      1 => int 2
    array (size=2)
      0 => int 1
      1 => int 2
    array (size=2)
      0 => int 1
      1 => int 2
*/
 
 
$t->reset();
  foreach(
$a as $p)
  {
   
$b = &$p;
   
$t->show($b);
  }
 
/* Output obtain:
    array (size=2)
      0 => int 1
      1 => int 2
    array (size=2)
      0 => int 3
      1 => int 4
    array (size=2)
      0 => int 5
      1 => int 6
*/
up
-5
pnc at balintx dot me
1 year ago
Just a simple strange behavior I have ran into:

If you accidentally put a semicolon after the foreach statement, you get no errors, but the loop will only run on the last element of the array:
<?php
$array
= array(1,2,3);
foreach (
$array as $key);
{
    echo
$key;
}
// output: 3
?>

Correctly:
<?php
$array
= array(1,2,3);
foreach (
$array as $key)
{
    echo
$key;
}
// output: 123
?>

It took me a while to find that semicolon.
up
-2
till at etill dot net
9 months ago
Note: Empty arrays are handled just fine by foreach, but for fail-safe code, you should always check that what is passed in fact is an array, like this:

<?php
if( is_array( $a) ) {
  foreach(
$a as $v) { ... }
} else
// $a is not an array
;
up
-8
Anteaus
2 years ago
"In order to be able to directly modify array elements within the loop precede $value with &. In that case the value will be assigned by reference. "

PLEASE CLARIFY! -Does this still hold true in php5.4+, where explicit passing by reference is seemingly forbidden- or is this now illegal syntax?
up
-11
liam666 at donnelly-house dot net
2 years ago
This is a decent, simple, and easy way to reference other values of an associative array when using foreach. (effective "next", "prev", etc.)
The only care that needs to be taken is if the array is HUGE in size, so you don't run into memory use problems. (and potential speed issues)

This example uses the 'primary' array, $aPublishSeq, which is ksort-ed to put the array in order according to the associative keys. The array is then copied using a foreach loop to make a duplicate array where the key and value order correspond to the first array, but the keys are sequential numeric starting at zero.

ksort ($aPublishSeq, SORT_STRING);     // put them all in the right order keeping array keys
foreach ($aPublishSeq as $aValue)
   $aPublishIdx[] = $aValue;          // duplicate array using corresponding sequential numeric keys

Now, in the usage foreach loop, an index variable is used to keep in sync with the associative array.

$PubIdx = -1;     // start at -1 to start at 0 below

foreach ($aPublishSeq as $sKey => $sValue) {

      ++$PubIdx;     // index into $aPublishIdx array of corresponding element in $aPublishSeq array (for "next" element check, etc.)

   echo $aPublishIdx[$PubIdx  - 1]     // previous array value
   echo $aPublishIdx[$PubIdx]          // current array value
   echo $aPublishIdx[$PubIdx  + 1]     // next array value

....

It's simple, but it works, and without much muss or fuss.
up
-35
Ashus
3 years ago
If you wondered how to create a list of all possible combinations of variable amount of arrays (multiple foreach), you might use this:

<?php

$a
[0] = array('a1','a2');
$a[1] = array('b1','b2','b3');
$a[2] = array('c1','c2');

function
getAllCombinations($a,$i,$s)
    {
    foreach (
$a[$i] as $v)
        {
        if (!isset(
$a[$i+1]))
            {
            echo
$s.$v."\n";
            } else {
           
getAllCombinations($a,$i+1,$s.$v);
            }
        }
    return
$s;
    }

echo
getAllCombinations($a,0,'');

?>

the result:

a1b1c1
a1b1c2
a1b2c1
a1b2c2
a1b3c1
a1b3c2
a2b1c1
a2b1c2
a2b2c1
a2b2c2
a2b3c1
a2b3c2
up
-44
simplex
10 years ago
"As of PHP 5, you can easily modify array's elements by preceding $value with &. This will assign reference instead of copying the value."

There are cases where array_walk or array_map are inadequate (conditional required) or you're just too lazy to write a function and pass values to it for use with array_map...

My solution to foreach for php 4 and 5 to modify values of an array directly:

<?php

$testarr
= array("a" => 1, "b" => 2, "c" => 3, "d" => 4);

$testarr_keys = array_keys($testarr);
$testarr_values = array_values($testarr);

for (
$i = 0; $i <= count($testarr) - 1; $i++) {
   
$testarr[$testarr_keys[$i]] = $testarr_values[$i] * 2;
}

print_r($testarr);
?>
up
-42
Voitcus at wp dot pl
5 years ago
You can even iterate through "dynamic" arrays that do not physically exist, but are objects that implement Iterator interface. They don't need to be stored in memory when foreach starts.

Consider the array that contains some values (I called it $allValues in the example below) and we want to have only some of them (eg. the ones that are dividable by 2). I create an object that would serve as dynamic array, that means it would "dynamically update" its values together with $allValues. The main advantage is that I store only one array, and it's the only array I serialize.

An object of MyIter class will not contain any values itself:
<?php
class MyIter implements Iterator { // you can implement ArrayAccess and Countable interfaces too, this will make class MyIter behave like a "real" array
 
private $position = 0; // an internal position of the current element
  // please note that $position has nothing common with $allValues!

 
private function getTable(){ // prepare a temporary "static" table of all objects in the class
   
global $allValues;
   
$result=array(); // temporary variable
   
foreach($allValues as $obj){
      if(
$obj % 2 == 0) // check if the value is even
       
$result[]=$obj; // if yes, I want it
     
}
    return
$result;
  }   

 
// the all below declared methods are public and belong to the Iterator interface
 
function rewind() { // a method to start iterating
   
$this->position = 0; // just move to the beginning
 
}

  function
current() { // retrieves the current element
   
$table=$this->getTable(); // let us prepare a table
   
return $table[$this->position]; // and return the current element
 
}

  function
key() { // retrieves the current element's key
   
return $this->position; // this is used by foreach(... as $key=>$value), not important here
 
}

  function
next() { // move to next element
   
++$this->position;
  }

  function
valid() { // check if the current element is valid (ie. if it exists)
   
return array_key_exists($this->position, $this->getTable());
  }
}
// end of class

// now prepare the array of 12 elements
$allValues=array(0,1,2,3,4,5,6,7,8,9,10,11);

//we would like to have a dynamic array of all even values
$iterator=new MyIter();

foreach(
$iterator as $value){
  echo
$value."<br />";
}
?>
This will result in:
0
2
4
6
8
10

(You may also like to see what var_dump($iterator) produces).

Another great advantage is that you can modify the main table "on-the-fly" and it has its impact. Let us modify the last foreach loop:
<?php
// ...all above shall stay as it was
foreach($iterator as $value){
  echo
$value."<br />";
  if(
$value==6){
   
$allValues=array(2,3);
    echo
"I modified source array!<br />";
  }
}
?>
This produces now:
0
2
4
6
I modified source array!

However, if you feel it is rather a catastrophic disadvantage (maybe for example, it shows the values 0, 4, and 6 which were removed when we reached 6), and wish to have a "static" array that will iterate even in modified objects, just call getTable() in rewind() method and save it in temporary (private perhaps) field. In my example getTable() is called every iteration, and it calls another foreach through $allValues, which together might be time-consuming. Consider what you need.
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