PHP Merge (Add) Two Arrays by Same Key

Question

I have two arrays.

$a = array('a' => 2, 'b' => 5, 'c' => 8);
$b = array('a' => 3, 'b' => 7, 'c' => 10);

I want to merge these two arrays and get following result.

$c = array('a' => 5, 'b' => 12, 'c' => 18);

What is the easiest way to archive this?

Thanks!

possible duplicate of [PHP Array Merge two Arrays on same key](http://stackoverflow.com/questions/14842272/php-array-merge-two-arrays-on-same-key) — Bruce, Jun 15 '15 at 11:10

score 1 · Answer 1 · answered Jun 15 '15 at 10:53

1

$c = array();
foreach ($a as $k => $v) {
    if (isset($b[$k])) {
        $c[$k] = $b[$k] + $v;
    }
}

You need to check whether keys exist in both arrays.

answered Jun 15 '15 at 10:53

marian0

3,336
3
27
37

Tommy Jinks · Accepted Answer · 2015-06-15T11:20:25.970

1

As mentioned in the comments, looping through the array will do the trick.

$a = array('a' => 2, 'b' => 5, 'c' => 8);
$b = array('a' => 3, 'b' => 7, 'c' => 10);
$c = array();
foreach($a as $index => $item) {
  if(isset($b[$index])) {
    $new_value = $a[$index] + $b[$index];
    $c[$index] = $new_value;
  }
}

edited Jun 15 '15 at 11:20

answered Jun 15 '15 at 10:53

Tommy Jinks

747
6
21

@VajiraLasantha Glad I could help :) – Tommy Jinks Jun 15 '15 at 11:00
What if the keys were not same – Narendrasingh Sisodia Jun 15 '15 at 11:02
@uchiha Good point. But both my arrays contains last 30 days as keys. – Vajira Lasantha Jun 15 '15 at 11:07
Its just a question you need a rigid output – Narendrasingh Sisodia Jun 15 '15 at 11:09
1

@Uchiha Great point. I've added an `isset` to solve this. This will merely ignore any other keys that are in `$a` but not in `$b`. This could get more complex by adding the new key to `$c`, however this doesn't fit the scenario of the question so I didn't add it. – Tommy Jinks Jun 15 '15 at 11:17
1

@Uchiha Missed a bracket. I shall blame this on it being a Monday morning! – Tommy Jinks Jun 15 '15 at 11:21
@Tommy It was monday night for me after a long day. May be that's why I could not figure out this easy method. :) I was just messing with some D3 stuff. – Vajira Lasantha Jun 15 '15 at 21:38

Faiz Rasool · Answer 3 · 2015-06-15T15:05:15.037

1

You can easily do this by foreach loop, please see the example below

$c = array();
$a = array('a' => 2, 'b' => 5, 'c' => 8);
$b = array('a' => 3, 'b' => 7, 'c' => 10);
foreach ($a as $key => $value) {
    $tmp_value = $a[$key] + $b[$key];
    $c[$key] = $tmp_value;
}
print_r($c);

edited Jun 15 '15 at 15:05

answered Jun 15 '15 at 10:54

Faiz Rasool

1,379
1
12
20

Why should the OP "try this"? Please add an explanation of what you did and why you did it that way, not only for the OP but for future visitors to SO. – Jay Blanchard Jun 15 '15 at 14:53

Narendrasingh Sisodia · Answer 4 · 2015-06-15T11:00:49.730

1

You can simply use foreach as

foreach($b as $key => $value){
    if(in_array($key,array_keys($a)))
        $result[$key] = $a[$key]+$value;

}

edited Jun 15 '15 at 11:00

answered Jun 15 '15 at 10:55

Narendrasingh Sisodia

21,247
6
47
54

PHP Merge (Add) Two Arrays by Same Key

4 Answers4