Why I'm not able to add new key value pair in an associative array?

Question

I've a large associative array titled $data. For your understanding I'm printing below one element from it.

Array
(
    [0] => Array
        (

            [id] => 92
            [zip_code] => 07080
            [phone_no] => 7327630062
            [amount] => 
            [currency] => $
            [product_details] => Array
                (
                )

        )
    [1] => Array
        (

            [id] => 93
            [zip_code] => 07081
            [phone_no] => 7327630063
            [amount] => 20
            [currency] => $
            [product_details] => Array
                (
                )

        )
)

Now I want to create a new key-value pair in every element of the above associative array titled $data. For it I wrote following logic but it's not creating a new key-value pair. Can someone please help me in this regard?

foreach($data as $key => $value) {
        if(!empty($value['amount'])) { 
          $value['final_amount'] = $value['amount'] - 2;
        } else 
          $value['final_amount'] = '';        
      }

When doing foreach, PHP creates copies so doing $value = something doesn't actually affect the original array — Jonathon
– Jonathon, Commented Aug 17, 2014 at 17:30
In addition, your array appears to be an indexed array of associative arrays. You could do for ($i=0; $i<count($data); $i++){ $data[$i]['something'] = 'something'; } — Jonathon
– Jonathon, Commented Aug 17, 2014 at 17:31
@Jonathon I agree with your first comment but i don't with second. The foreach loop works — Justin Iurman
– Justin Iurman, Commented Aug 17, 2014 at 17:33
@Jonathon That would add the overhead of calling the count() function on every iteration of the loop. — theftprevention
– theftprevention, Commented Aug 17, 2014 at 17:36

Karoly Horvath · Accepted Answer · 2014-08-17 17:33:20Z

5

From the manual of foreach:

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.

foreach($data as $key => &$value)

answered Aug 17, 2014 at 17:33

Karoly Horvath

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2 Comments

yitwail Over a year ago

Manual also contains this warning, which is good practice:

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

In this case, an unset($value); statement should be added right below the loop.

Karoly Horvath Over a year ago

@yitwail: I see that as noise. If the scope of the $value isn't clear at first glance, you probably should do some refactoring anyways.

theftprevention · Accepted Answer · 2014-08-17 17:31:37Z

3

In the foreach loop, pass the $value by reference by adding an ampersand & before the variable name:

foreach($data as $key => &$value)

This will allow the loop to modify the original $data instead of modifying a copy of it.

answered Aug 17, 2014 at 17:31

theftprevention

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