array merge with multidimensional array

Question

I have this simple setup:

$array1 = array(0 => array(0 => array('amount' => '49')));
$array2 = array(0 => array(0 => array('amount' => '149')));

$mergetest = array_merge_recursive($array1, $array2);

This outputs:

array(2) {
  [0]=>
  array(1) {
    [0]=>
    array(1) {
      ["amount"]=>
      string(2) "49"
    }
  }
  [1]=>
  array(1) {
    [0]=>
    array(1) {
      ["amount"]=>
      string(3) "149"
    }
  }
}

It should merge in such way, that the output should be like this instead:

    array(1) {
      [0]=>
      array(2) {
        [0]=>
        array(1) {
          ["amount"]=>
          string(2) "49"
        }
        [1]=>
        array(1) {
          ["amount"]=>
          string(3) "149"
        }
      }
    }

Since array index 0 already exists, and so does the array inside it - so it should match by child array instead of parent and in that way add the next child array to it.

Can this be done in a clean way without building a custom function that loops through and checks?

UPDATE

A solution, that also works with:

$array1 = array(0 => array(0 => array('amount' => '49')));
$array2 = array(1243 => array(0 => array('amount' => '49'), 1 => array('amount' => '449')));

Where the output is expected to be in separate parent arrays (0 and 1243), just like the first above output.

from PHP manual: "If the input arrays have the same string keys": the keys must be string keys (and not numeric indexes) for array_merge_recursive to fuse the rows — Kaddath
– Kaddath, Commented Oct 25, 2017 at 10:15
I think you could merge the 2 inner arrays like you did and then add them to the outer array? e.g. $array1 = array(0 => array('amount' => '49'))); $array2 = array(0 => array('amount' => '149'))); $innermerge = array_merge_recursive($array1, $array2); $mergetest = array(0 => $innermerge); — Filnor
– Filnor, Commented Oct 25, 2017 at 10:16
Rather than 1 and a half minimal reproducible examples, it would be better to re-do this question and post one definitive, completed minimal reproducible example to make the question clear and concise. — mickmackusa
– mickmackusa ♦, Commented Sep 23, 2022 at 13:36

Mad Angle · Accepted Answer · 2017-10-25 11:02:57Z

1

<?php
     $array1 = array(0 => array(0 => array('amount' => '49')));
     $array2 = array(0 => array(0 => array('amount' => '149')));

     $result = array_map('array_merge', $array1, $array2);
     var_dump($result);    
?>

And the output will be like the below.

array(1) {
  [0]=>
  array(2) {
    [0]=>
    array(1) {
      ["amount"]=>
      string(2) "49"
    }
    [1]=>
    array(1) {
      ["amount"]=>
      string(3) "149"
    }
  }
}

NOTE : array_merge_recursive() will fail because it appends numeric keys, not merging them:

UPDATE ANSWER FOR ARRAYS WITH DIFFERENT INDEXES

    <?php
        $array1 = array(0 => array(0 => array('amount' => '49')));
        $array2 = array(1243 => array(0 => array('amount' => '49'), 1 => array('amount' => '449')));
        $keys = array_unique(array_merge(array_keys($array1), array_keys($array2)));

        foreach ($keys as $key) {
          if (array_key_exists($key, $array1) && array_key_exists($key, $array2)) {
            $array3[$key] = array_merge($array1[$key], $array2[$key]);
          } elseif (array_key_exists($key, $array1)) {
            $array3[$key] = $array1[$key];
          } else {
            $array3[$key] = $array2[$key];
          }
        }


        var_dump($array3);
?>

And the output will be

array(2) {
  [0]=>
  array(1) {
    [0]=>
    array(1) {
      ["amount"]=>
      string(2) "49"
    }
  }
  [1243]=>
  array(2) {
    [0]=>
    array(1) {
      ["amount"]=>
      string(2) "49"
    }
    [1]=>
    array(1) {
      ["amount"]=>
      string(3) "449"
    }
  }
}

edited Oct 25, 2017 at 11:02

answered Oct 25, 2017 at 10:36

Mad Angle

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4 Comments

Karem Over a year ago

Thanks for this! Could you maybe explain why array_map('array_merge', $..) works over normal array_merge?

Karem Over a year ago

I have now tried this, and seems like this doesn't work as expected if the parent index have a different index, it still adds to the same child. I will update with another example.

Mad Angle Over a year ago

@Karem I have updated the anwer. Please check whether its working for you.

Karem Over a year ago

Great! Works in both use cases! Thanks and I suppose there isn't a default function for this, therefore the need of a foreach.

Rad80 · Accepted Answer · 2017-10-25 10:23:19Z

0

You can get the result you want if you use string keys at the top level rather than integers.

You have two levels of integer-indexed arrays but it seems that to you they have a different nature because you need them to be merged differently. PHP has no way to know that, so with this setup no standard function can do what you need. You will need to change the data structure to mark that difference (e.g. by using string keys on first level and integers on the second) or write a custom merge function here.

answered Oct 25, 2017 at 10:23

Rad80

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