How to use array_map with reset callback in php 8 [duplicate] - php

Question

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Closed 10 months ago.
I have a function that work good in php 7 but in php 8.0.11 has warning
$orders->result = array_map('reset', $orders->result);
E_WARNING: reset(): Argument #1 ($array) must be passed by reference, value given in
Of course, I can use this code instead that but maybe slower than array_map
foreach ($orders->result as $item)
$result[$item[0]['order_id']] = $item[0];
Edit:
before foreach or array_map the output like this
Array
(
[0] => Array
(
[order_id] => 41111909
[shop_id] => 34277
[user_id] => 42363
[status_id] => 4
)
)
after use foreach output like this
Array
(
[41111909] => Array
(
[order_id] => 41111909
[shop_id] => 34277
[user_id] => 42363
[status_id] => 4
)
)
How to solve it ?

Answer 1

The simplest replacement is to make an arrow function (single-expression closure) to get the element for you.
If the arrays are plain lists, so that you're always getting element 0, that's as simple as:
$orders->result = array_map(fn($item) => $item[0], $orders->result);
Another alternative in this case is array_column:
$orders->result = array_colum($orders->result, 0);
If you have other keys, you could use either reset or array_key_first in the callback instead:
$orders->result = array_map(fn($item) => $item[array_key_first($item)], $orders->result);
(I suspect array_key_first will be slightly more efficient, since it doesn't need to manipulate the internal array pointer.)

Answer 2

It's not entirely clear what you're trying to do, but it seems like you are trying to get the first value from nested arrays. You should be able to use a function:
$orders->result = array_map(function($v) { return reset($v); }, $orders->result);
You may also try using current if it does what you need as it doesn't take a reference and the array pointer should already be reset by array_map:
$orders->result = array_map('current', $orders->result);
After the edit the code in question is not re-indexing the array as you show in the before and after. To do that is simple:
$orders->result = array_column($orders->result, null, 'order_id');