How to merge subarray in PHP most easily?

0 votes
asked Jan 26, 2010 by user198729
$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.

6 Answers

0 votes
answered Jan 26, 2010 by sprugman
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);
0 votes
answered Jan 26, 2010 by felix-kling

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.

0 votes
answered Jan 26, 2010 by bish

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));
0 votes
answered Jan 31, 2012 by goce-ribeski

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

0 votes
answered Jan 27, 2014 by 23w

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());
0 votes
answered Sep 15, 2017 by gannet

For PHP 5.6 with splat operator:

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