PHP reduce and merge? an array in several steps

Question

I'm trying to reduce/merge an array looking like this

$test = Array
(
    [0] => Array
        (
            [id] => 150023
            [rowtext] => part 1
            [rowpartnumber] => 4360
            [qty] => 2.00
            [min_delper] => 2021-07-28
        )

    [1] => Array
        (
            [id] => 150026
            [rowtext] => part 2
            [rowpartnumber] => 4360
            [qty] => 2.00
            [min_delper] => 2021-07-29
        )

    [2] => Array
        (
            [id] => 150023
            [rowtext] => part 3
            [rowpartnumber] => 4361
            [qty] => 4.00
            [min_delper] => 2021-08-22
        )

    [3] => Array
        (
            [id] => 150023
            [rowtext] => part 4
            [rowpartnumber] => 4362
            [qty] => 2.00
            [min_delper] => 2021-09-22
        )

);

I want to sum the [qty] where [rowpartnumber] are the same, I can achieve this with

$summa_test = array_reduce($test, function ($a, $b) {
  isset($a[$b['rowpartnumber']]) ? $a[$b['rowpartnumber']]['qty'] += $b['qty'] : $a[$b['rowpartnumber']] = $b;  
  return $a;
});

But I would also like to take the [id] where [rowpartnumer] are the same and add it to [id] so the output should look like this:

Array
(
    [0] => Array
        (
            [id] => 150023 150026
            [rowtext] => part 1
            [rowpartnumber] => 4360
            [qty] => 4.00
            [min_delper] => 2021-07-28
        )

    [1] => Array
        (
            [id] => 150023
            [rowtext] => part 3
            [rowpartnumber] => 4361
            [qty] => 4.00
            [min_delper] => 2021-08-22
        )

    [2] => Array
        (
            [id] => 150023
            [rowtext] => part 4
            [rowpartnumber] => 4362
            [qty] => 2.00
            [min_delper] => 2021-09-22
        )

);

Can't seem to get my head around it, so a little help from you experts would be great, thank you

Peter Koltai · Accepted Answer · 2021-07-28 11:10:25Z

1

You have to modify the callback function to concatenate the id to the previous one if the rowpartnumber already exits. Like this:

$summa_test = array_reduce($test, function ($carry, $item) {
  if (isset($carry[$item['rowpartnumber']])) {
      $carry[$item['rowpartnumber']]['qty'] += $item['qty'];
      $carry[$item['rowpartnumber']]['id'] .= " ".$item['id'];
  }
  else {
      $carry[$item['rowpartnumber']] = $item;
  }
  return $carry;
});

I don't know whether it is a problem, but because of the concatenation id will become a string where multiple ids are found - but remains integer when only one. If it is a problem for you, there are two options:

Convert to string even if only one id
Use an array to store to multiple ids.

(I changed the parameter names to the ones used in PHP documentation - you can change it back, but generally it is a good idea to keep that way - others will more easily understand your code.)

edited Jul 28, 2021 at 11:10

answered Jul 28, 2021 at 8:47

Peter Koltai

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1 Comment

wall3 Over a year ago

Awesome, that is exactly what I was looking for, regarding the id its not going to be a problem if it's a string for me. And thank you for excellent educational explanation

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