How to merge subarray values and remove duplicates?

Question

$arr[] = array('A','B');
$arr[] = array('C','B');
...

I need to get the merged result of all sub array of $arr .

And for duplicated entries,should fetch only one.

score 25 · Answer 1 · answered Jan 26 '10 at 19:49

25

If you really don't want to loop, try this:

$arr[] = array('A','B');
$arr[] = array('C','B');
$arr[] = array('C','D');
$arr[] = array('F','A');
$merged = array_unique(call_user_func_array('array_merge', $arr));

answered Jan 26 '10 at 19:49

bish

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I think there is no need for `array_unique` as `array_merge` will overwrite duplicate keys if found any. Can anybody please reply me? – Ankit Apr 02 '16 at 05:17
without the 'array_merge' the following error comes up "ErrorException: call_user_func_array() expects exactly 2 parameters" @Ankit – LeRoy Apr 26 '16 at 11:28
genius, one of the rare cases when we can actually use call_user_func_array and it's like a perfect fit for this kind of thing. – Robert Sinclair Aug 16 '17 at 00:22

score 15 · Answer 2 · edited Mar 02 '17 at 16:41

OK through another question I found out that the following is actually possible (I tried myself without success, I had the wrong version) if you use PHP version >= 5.3.0:

$merged_array = array_reduce($arr, 'array_merge', array());

If you only want unique values you can apply array_unique:

$unique_merged_array = array_unique($merged_array);

This works if you only have flat elements in the arrays (i.e. no other arrays). From the documentation:

Note: Note that array_unique() is not intended to work on multi dimensional arrays.

If you have arrays in your arrays then you have to check manually e.g. with array_walk:

$unique_values = array();

function unique_value($value, &$target_array) {
    if(!in_array($value, $target_array, true))
        $target_array[] = $value;
}

array_walk($merged_values, 'unique_value', $unique_values);

I think one can assume that the internal loops (i.e. what array_walk is doing) are at least not slower than explicit loops.

I don't think $merged_array = array_merge($arr); will actually break up the sub-arrays, which I'm pretty sure is what the OP was asking for. — sprugman, Jan 26 '10 at 18:14
Worth noting that array_merge should be in quotes e.g. 'array_merge' — Matthew Riches, Jan 03 '14 at 11:55

sprugman · Answer 3 · 2010-01-27T23:47:10.647

8

array_unique(array_merge($arr[0], $arr[1]));

or for an unlimited case, I think this should work:

$result_arr = array();
foreach ($arr as $sub_arr) $result_arr = array_merge($result_arr, $sub_arr);
$result_arr = array_unique($result_arr);

edited Jan 27 '10 at 23:47

answered Jan 26 '10 at 15:54

sprugman

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It can have more than 2 sub arrays. – user198729 Jan 26 '10 at 15:55
The number of sub arrays is dynamic. – user198729 Jan 26 '10 at 15:57
Despite the author only giving $arr 0 + 1 as an example, I think they needs a solution to accommodate for all child items of $arr. – Ben Everard Jan 26 '10 at 15:57
Is there a way to do it other than loop? – user198729 Jan 26 '10 at 15:59
why? what's wrong with a loop? I suppose you could use some kind of mapping function. Look at the array section of the php docs for other ideas. http://www.php.net/manual/en/ref.array.php – sprugman Jan 26 '10 at 16:00
If the number of arrays are dynamic, I think loops could be the best choice. Why would you not want a loop? – Anthony Forloney Jan 26 '10 at 16:00
Is there a array function that can handle this problem? – user198729 Jan 26 '10 at 16:01
array_walk() is a possibility, but it's more overhead – sprugman Jan 26 '10 at 16:03
It is still not correct, it has to be `$result_arr = array_merge($result_arr, $sub_arr);` – Felix Kling Jan 27 '10 at 14:09

score 1 · Answer 4 · answered Nov 27 '14 at 12:53

1

This answer is based on Felix Kling post. It's more accurate version with fixing "non array" sub-elements.

$res = array_reduce($res, function(&$res, $v) {
                            return array_merge($res, (array) $v);
                        }, array());

answered Nov 27 '14 at 12:53

23W

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Great solution and use array_filter() to get rid of empty array elements caused by empty array values or strings added previously. Here is the final version: $res = array_filter(array_reduce($res, function(&$res, $v) {return array_merge($res, (array) $v);}, array())); – Tarik Oct 23 '16 at 21:42

score 1 · Answer 5 · answered Sep 12 '17 at 03:05

1

For PHP 5.6 with splat operator:

array_unique(array_merge(...$arr));

answered Sep 12 '17 at 03:05

Gannet

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score 1 · Answer 6 · edited Nov 24 '19 at 17:28

1

A simple way to handle this in PHP Version >= 5.6 is to use the splat operator also called Argument Unpacking.

$arr = array_unique(array_merge(...$arr));

edited Nov 24 '19 at 17:28

wnull

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answered Nov 22 '17 at 15:56

Mat Lipe

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score 1 · Answer 7 · answered Jan 31 '12 at 13:34

1

$merged_array = array_reduce($serp_res, 'array_merge', array()); with added quotas,'array_merge', worked for me.

answered Jan 31 '12 at 13:34

Goce Ribeski

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How to merge subarray values and remove duplicates?

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