Changing value inside foreach loop doesn't change value in the array being iterated over [duplicate]

Question

Why does this yield this:

foreach( $store as $key => $value){
$value = $value.".txt.gz";
}

unset($value);

print_r ($store);

Array
(
[1] => 101Phones - Product Catalog TXT
[2] => 1-800-FLORALS - Product Catalog 1
)

I am trying to get 101Phones - Product Catalog TXT.txt.gz

Thoughts on whats going on?

EDIT: Alright I found the solution...my variables in my array had values I couldn't see...doing

$output = preg_replace('/[^(\x20-\x7F)]*/','', $output);
echo($output);

Cleaned it up and made it work properly

Michel · Accepted Answer · 2017-01-18 10:29:00Z

41

The doc http://php.net/manual/en/control-structures.foreach.php clearly states why you have a problem:

"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."

<?php
$arr = array(1, 2, 3, 4);
foreach ($arr as &$value) {
    $value = $value * 2;
}
// $arr is now array(2, 4, 6, 8)
unset($value); // break the reference with the last element
?>

Referencing $value is only possible if the iterated array can be referenced (i.e. if it is a variable). The following code won't work:

<?php
/** this won't work **/
foreach (array(1, 2, 3, 4) as &$value) {
    $value = $value * 2;
}
?>

edited Jan 18, 2017 at 10:29

answered Mar 29, 2012 at 7:15

Michel

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2 Comments

user1179295 Over a year ago

I am still getting this when I follow your first example: Array ( .txt.gz => 101Phones - Product Catalog TXT .txt.gz => 1-800-FLORALS - Product Catalog 1 ) why is it assigning my key as the text I am adding to the variable?

RaKXeR Over a year ago

if anyone happens to stumble into this like I did after me, this is the solution to this question most of the time. OP, consider marking this as the right answer, if you ever login again...

Andy · Accepted Answer · 2012-03-29 07:13:34Z

6

Try

foreach( $store as $key => $value){
    $store[$key] = $value.".txt.gz";
}

answered Mar 29, 2012 at 7:13

Andy

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Comments

deceze · Accepted Answer · 2012-03-29 07:14:56Z

6

The $value variable in the array is temporary, it does not refer to the entry in the array.
If you want to change the original array entry, use a reference:

foreach ($store as $key => &$value) {
                       //  ^ reference
    $value .= '.txt.gz';
}

answered Mar 29, 2012 at 7:14

deceze♦

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3 Comments

user1179295 Over a year ago

When I do that it gives me: Array ( .txt.gz => 101Phones - Product Catalog TXT .txt.gz => 1-800-FLORALS - Product Catalog 1 )

deceze Over a year ago

It should certainly not do that. Post the full code that produces that result.

user1179295 Over a year ago

I just realized it is something weird from my variables ....I created an array $stores=array("tree","boat"); and it worked...whats a good way to remove unseen characters?

Daniel · Accepted Answer · 2012-03-29 07:12:24Z

4

You are rewriting the value within the loop, and not the key reference in your array.

Try

 $store[$key] = $value.".txt.gz";

answered Mar 29, 2012 at 7:12

Daniel

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Comments

k102 · Accepted Answer · 2012-03-29 07:15:22Z

3

pass $value as a reference:

foreach( $store as $key => &$value){
   $value = $value.".txt.gz";
}

answered Mar 29, 2012 at 7:15

k102

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Comments

Baba · Accepted Answer · 2012-03-29 07:16:40Z

3

Try

$catalog = array();

foreach( $store as $key => $value){
    $catalog[] = $value.".txt.gz";
}


print_r ($catalog);

OR

foreach( $store as $key => $value){
    $store[$key] = $value.".txt.gz";
}


print_r ($store);

Depends on what you want to achieve

Thanks :)

answered Mar 29, 2012 at 7:16

Baba

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1 Comment

user1179295 Over a year ago

Its omitting the .txt.gz Array ( [1] => 101Phones - Product Catalog TXT [2] => 1-800-FLORALS - Product Catalog 1 )

Chibueze Opata · Accepted Answer · 2012-03-29 07:19:18Z

2

I believe this is what you want to do:

foreach( $store as $key => $value){
$store[$key] = $value.".txt.gz";
}

unset($value);

print_r ($store);

answered Mar 29, 2012 at 7:19

Chibueze Opata

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Comments

Jarosław Gomułka · Accepted Answer · 2012-03-29 08:27:01Z

2

How about array map:

$func = function($value) { return $value . ".txt.gz"; };
print_r(array_map($func, $store));

edited Mar 29, 2012 at 8:27

answered Mar 29, 2012 at 7:16

Jarosław Gomułka

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Comments

Rahil Wazir · Accepted Answer · 2014-01-28 12:31:08Z

2

foreach(array_container as & array_value)

Is the way to modify array element value inside foreach loop.

edited Jan 28, 2014 at 12:31

Rahil Wazir

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answered Jan 28, 2014 at 11:56

Ankush Jetly

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