PHP array merge on Inner keys

Question

I have two arrays like:

$a = [
    0 => [
        'price' => 5.5
    ],
    1 => [
        'price' => 6.0
    ],
    2 => [
        'price' => 6.2
    ],
    3 => [
        'price' => 6.5
    ],
];

$b = [
    0 => [
        'color' => 'RED'
    ],
    1 => [
        'color' => 'WHITE'
    ],
    2 => [
        'color' => 'BLUE'
    ],
    3 => [
        'color' => 'RED'
    ],
];

I should have this response:

Array
(
    [0] => Array
        (
            [price] => 5.5
            [color] => RED
        )
    [1] => Array
        (
            [price] => 6
            [color] => WHITE
        )
    [2] => Array
        (
            [price] => 6.2
            [color] => BLUE
        )
    [3] => Array
        (
            [price] => 6.5
            [color] => RED
        )
)

I heard about the function: array_merge_recursive but the response wasn't the requiered:

Array
(
    [0] => Array
        (
            [price] => 5.5
        )
    [1] => Array
        (
            [price] => 6
        )
    [2] => Array
        (
            [price] => 6.2
        )
    [3] => Array
        (
            [price] => 6.5
        )
    [4] => Array
        (
            [color] => RED
        )
    [5] => Array
        (
            [color] => WHITE
        )

    [6] => Array
        (
            [color] => BLUE
        )
    [7] => Array
        (
            [color] => RED
        )
    )

so I decided to write my own function:

function merge ($a, $b) {
    $keys = array_keys($a);
    foreach ($keys as $value) {
        if (isset($b[$value])) {
            $tmp = array_keys($b[$value]);
            foreach ($tmp as $val){
                $a[$value][$val] = $b[$value][$val];
            }
        }
    }
    return $a;
}
print_r(merge($a, $b));

and I got the proper response:

Array
(
    [0] => Array
        (
            [price] => 5.5
            [color] => RED
        )
    [1] => Array
        (
            [price] => 6
            [color] => WHITE
        )
    [2] => Array
        (
            [price] => 6.2
            [color] => BLUE
        )
    [3] => Array
        (
            [price] => 6.5
            [color] => RED
        )
)

The problem is that it works fine for little arrays but doesn't work good for big arrays, so my question is: how could I optimize the function? because the complexity would grow depending on merged keys.

Using PHP 7.0

M. Eriksson · Accepted Answer · 2017-08-14 15:17:14Z

4

You can use array_replace_recursive() instead.

array_replace_recursive($a, $b);

Demo: https://3v4l.org/bFIZ2

answered Aug 14, 2017 at 15:17

M. Eriksson

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2 Comments

AbraCadaver Over a year ago

Probably faster, I forgot that one.

Pedro Rodriguez Larez Over a year ago

Yes this is a lot faster and complies perfectly!

AbraCadaver · Accepted Answer · 2017-08-14 15:15:42Z

4

You need to check that they are the same length and then one simple foreach is all that is needed:

foreach($a as $k => $v) {
    $result[$k] = array_merge($v, $b[$k]);
}

answered Aug 14, 2017 at 15:15

AbraCadaver

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2 Comments

Pedro Rodriguez Larez Over a year ago

there can be several keys to merge, and the array lengths may not be the same.

AbraCadaver Over a year ago

Magnus has the best one.

marmeladze · Accepted Answer · 2017-08-14 15:18:06Z

0

the simple solution might be,

$c = [];

for($i=0; $i<count(array_keys($a)); $i++) {
  $c[$i] =array_merge($a[$i], $b[$i]);
}

print_r($c);

https://repl.it/KJNL

answered Aug 14, 2017 at 15:18

marmeladze

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