php Multidimensional Array for key and get value

Question

I have the following code sample:

$arr = array(
  array(
    'packid'=> '1', 'total' => '30'),
  array(
    'packid'=> '2', 'total' => '20')
);

$arr is in a loop

 foreach ($pack->memberPack as $memPack) {
            if($memPack->packId = $search_arr_key)
            //get the `total` value then do something
        }

and $memPack object like this:

array(1) {
["memberPack"]=>
array(1) {
  [0]=>
  object(MemberPack)#290 (6) {
    ["errors"]=>
    NULL
    ["attributes":"ActiveRecord\Model":private]=>
    array(3) {
      ["memberPackId"]=>
      int(1)
      ["packId"]=>
      int(1)
      ["memberId"]=>
      int(14369)
    }  
  }
}

}

How can i search the key packId equal to $memPack->packId and get the match total? (ex. if packId =2 and get the value 20 )

Do you mean besides a loop?

Rasclatt
– Rasclatt

2016-12-30 03:18:27 +00:00
Commented Dec 30, 2016 at 3:18 — Rasclatt
– Rasclatt, Commented Dec 30, 2016 at 3:18
updated the question, the $arr is in a loop

Doran Wu
– Doran Wu

2016-12-30 03:34:17 +00:00
Commented Dec 30, 2016 at 3:34 — Doran Wu
– Doran Wu, Commented Dec 30, 2016 at 3:34

Doran Wu · Accepted Answer · 2016-12-30 06:20:23Z

1

For better performance, here is a good implementation.

$array = array_combine(array_column($arr, 'packId'), array_column($arr, 'total'));
$total = $array[$memPack->packId];

edited Dec 30, 2016 at 6:20

Doran Wu

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answered Dec 30, 2016 at 4:03

LF-DevJourney

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Comments

sebasaenz · Accepted Answer · 2016-12-30 03:26:06Z

1

I think you are looking for a loop that finds the result according to the packid you select.

<?php

$arr = array(
  array(
    'packid'=> '1', 'total' => '30'),
  array(
    'packid'=> '2', 'total' => '20')
);

$whateverPackidYouWant = 2;
$answer;

for ($i = 0; $i < count($arr); $i++) {

if ($arr[$i]['packid'] == $whateverPackidYouWant) {
   $answer = $arr[$i]['total'];
}

}

echo $answer;

?>

Please let me know if this is what you were looking for.

answered Dec 30, 2016 at 3:26

sebasaenz

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Comments

Ruslan Osmanov · Accepted Answer · 2016-12-30 03:38:50Z

Simply iterate the array and check if the subarray contains the matching packid and total items. Break the loop on the first match:

$packid = 2;

foreach ($arr as $k => $v) {
  if ($v['packid'] == $packid && isset($v['total'])) {
    $total = $v['total'];
    break;
  }
}

Another approach (less optimal, but may look elegant to some people):

$key = array_search($packid, array_column($arr, 'packid'));
if ($key !== false && isset($arr[$key]['total'])) {
  $total = $arr[$key]['total'];
}

where array_column builds an array from the packid values ([1, 2]) in the order that matches the order of subarrays in $arr; array_search returns the index of the first occurrence of $packid in the array of packid values (and thus, the key of the subarray in $arr). The rest of the code fetches the total.

I have added this example for completeness. Don't use it as it is suboptimal.

THX, but I wonder why the second approach is less optimal ? can see some statistical number?
@DoranWu, array_column builds an array from all the items in $arr (O(n)). Then array_search, in worst case, iterates all the items in the generated array (O(n)). Thus, in the worst case it is a O(2n) operation. And the first approach (foreach) breaks the loop on the first match which is O(n) in worst case. Besides, the code with array_search and array_column is less readable, and even less flexible

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