Merging multiple associative arrays in PHP

Question

I'm not quite sure how to do this. Let's say I have 2 associative arrays

$arr1 = array('a' => "1", 'b' => "2", 'c' => "3");
$arr2 = array('a' => "9", 'b' => "8", 'c' => "7");

How could I possibly produce an "add-up" array as below

$arr1 = array(
  array('a', "1", "9"),
  array('b', "2", "8"),
  array('c', "3", "7")
);

I'm not sure if the above syntax is correct. If it's not, then an add-up that looks like below will do too

$arr1 = array(
  'a' => array("1", "9"),
  'b' => array("2", "8"),
  'c' => array("3", "7")
);

Thanks

@SilentGhost, Probably. I don't have much experience with multiple nested levels of associative arrays. But your format should do the job too. — drummer
– drummer, Commented Oct 28, 2009 at 18:11

SilentGhost · Accepted Answer · 2009-10-28 18:12:58Z

3

foreach($arr1 as $k=>$v) {
    $new[$k] = array($v, $arr2[$k]);
}

Is what I think you want. But if I'm mistaken, then you could do:

foreach($arr1 as $k=>$v) {
    $new[] = array($k, $v, $arr2[$k]);
}

answered Oct 28, 2009 at 18:12

SilentGhost

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3 Comments

Ben Reisner Over a year ago

your second form will generate what he was looking for. This assumes that both associative arrays will have the same keys.

SilentGhost Over a year ago

true, it never been intended to be more sophisticated. It's fairly easy to do produce more general solution, not sure OP needs it.

drummer Over a year ago

Thanks to both of you :) I tested, and it looks like Ben's answer fits it better, but I still have a small bug with the blanks. I'll open another question

Ben Reisner · Accepted Answer · 2009-10-28 18:14:02Z

0

$arr1 = array('a' => "1", 'b' => "2", 'c' => "3");
$arr2 = array('a' => "9", 'b' => "8", 'c' => "7");

$summ=array();
foreach(array($arr1,$arr2) as $arr){
    $keys=array_keys($arr);
    foreach($keys as $key){
        if(isset($summ[$key]))
            $summ[$key][]=$arr[$key];
        else $summ[$key]=array($arr[$key];
    }
}
/*
This will have made:
$sum = array(  
    'a' => array("1", "9"),  
    'b' => array("2", "8"),  
    'c' => array("3", "7")
);

I leave it up to you to now reduce this one more step to match your desired output.
*/

answered Oct 28, 2009 at 18:14

Ben Reisner

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2 Comments

Ben Reisner Over a year ago

SilentGhost had the better one if it is just 2 arrays and they have the same keys. If the keys may vary or you need to scale from 2 arrays then this is closer to what you need.

drummer Over a year ago

Good point. I think they probably may vary. For example 1 array could have a b d (no c), but the other a b c (no d). In this case, I will need it as a b c d but with blanks inserted for whatever is missing for one or the other. You say this will do better than the other?

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