Update array value in foreach loop

Question

I have this piece of code :

$start = ['23','', 'what'];
foreach($start as $i){
  if($i ==''){
    $i = 'satisfaction';
  }
}
print_r($start);

The output is :

Array
(
[0] => 23
[1] => 
[2] => what
)

Why did index [1] not get replaced with 'satisfaction'. In other words : I don't want to create a new array, but change the index of an existing array. Actually, what I'm trying to achieve is to do intval() on those indexes that are not empty (since intval on an empty index returns 0, which is not what I want).

print_r($i); and check the result – Saty May 12 '15 at 13:59 — Saty, May 12 '15 at 13:59
try $start[$i] = 'satisfaction'; – dbinns66 May 12 '15 at 13:59 — dbinns66, May 12 '15 at 13:59

Kevin · Answer 1 · 2015-05-12T14:08:40.933

3

According to the manual:

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.

So in your case, you should add &:

$start = ['23','', 'what'];
foreach($start as &$i){
               // ^ reference
    if($i === ''){
        $i = 'satisfaction';
    }
}

Sidenote: If your intent is to change those numeric values into data type integer, you can use (as you stated) intval or a simple type cast.

$start = ['23','', 'what'];
foreach($start as &$i){
    if(is_numeric($i)){
        $i = (int) $i;
    }
}

var_dump($start);

edited May 12 '15 at 14:08

answered May 12 '15 at 14:00

Kevin

41,694
12
53
70

1

OP's jumped on the *runaway train* bound for Cleveland. – Funk Forty Niner May 12 '15 at 16:08
looks it to be. oh well, I guess maybe the E-train will take them back ;-) – Funk Forty Niner May 13 '15 at 01:00

score 2 · Answer 2 · edited May 12 '15 at 14:03

2

Because foreach(...) acts "a bit" as a read-only iterator. If you want to modify elements, you'll have to access by reference.

example :

foreach ($start as &$i) {

}

For more info, see doc : http://php.net/manual/fr/control-structures.foreach.php

edited May 12 '15 at 14:03

Funk Forty Niner

74,450
15
68
141

answered May 12 '15 at 14:00

Cr3aHal0

809
4
11

Dan · Answer 3 · 2015-05-12T14:20:20.973

1

In your example you are just setting the variable $i, which is just a temporary variable for the loop. Instead, keep the array key in the loop and use that to set the value in the array:

$start = ['23','', 'what'];
foreach($start as $k=>$i){
  if($i ==''){
     $start[$k] = 'satisfaction';
  }
}

edited May 12 '15 at 14:20

answered May 12 '15 at 14:04

Dan

10,614
5
24
35

This's much better than using a reference. – Junius L May 12 '15 at 14:12

Update array value in foreach loop

3 Answers3