Add an array into another array if certain indexes match php - php

Question

I have an two arrays in php, what i would like to do is if drug_ids match, I want to add the second array as a sub array.
What I have
Array
(
[0] => Array
(
[drug_id] => 1
[drug] => Abacavir 300mg - Tabs
)
[1] => Array
(
[drug_id] => 4
[drug] => Abacavir/Lamivudine 120/60mg - FDC Tabs
)
[2] => Array
(
[drug_id] => 3
[drug] => Abacavir/Lamivudine 600/300mg - FDC Tabs
)
);
The second array with more data
Array
(
[0] => Array
(
[id] => 2
[decision_date] => 2018-08-10
[discussion] => The product is at 2.6 MOS
[recommendation] => recommendation
[drug_id] => 1
[created] => 2018-08-16 09:23:09
[user] => System Admin
)
[1] => Array
(
[id] => 3
[decision_date] => 2018-08-10
[discussion] => recommendation.
[recommendation] =>recommendation.
[drug_id] => 4
[created] => 2018-08-16 09:23:09
[user] => System Admin
)
[2] => Array
(
[id] => 4
[decision_date] => 2018-08-10
[discussion] => The product is at 6MOS.
[recommendation] =>ggfgfg.
[drug_id] => 4
[created] => 2018-08-16 09:23:09
[user] => System Admin
)
);
I would like to push the second array into the first one as decisions if drug ids match to create a final array
[0] => Array
(
[drug_id] => 4
[drug] => Abacavir/Lamivudine 120/60mg - FDC Tabs
[decisions] => Array(
[0] => Array
(
[id] => 3
[decision_date] => 2018-08-10
[discussion] => recommendation.
[recommendation] =>recommendation.
[drug_id] => 4
[created] => 2018-08-16 09:23:09
[user] => System Admin
)
[1] => Array
(
[id] => 4
[decision_date] => 2018-08-10
[discussion] => The product is at 6MOS.
[recommendation] =>ggfgfg.
[drug_id] => 4
[created] => 2018-08-16 09:23:09
[user] => System Admin
)
)
)
Any suggestions as to how this can be achieved?
What i have tried
$table_data //first array
$table_data //second array
foreach ($table_data as $mt) {
foreach ($items as $it) {
if ($it['drug_id'] == $mt['drug_id']) {
$decision['decisions'] = $it;
array_push($table_data, $decision);
}
}
}
//This does not work

Answer 1

There's a bug. Try the following
foreach ($table_data as &$mt) {
foreach ($items as $it) {
if ($it['drug_id'] == $mt['drug_id']) {
if (!isset($mt['decisions'])) {
$mt['decisions'] = [];
}
$mt['decisions'][] = $it;
}
}
}

Answer 2

Another way:
foreach ($arr1 as &$a) {
$a["decisions"] = array_filter($arr2, function ($b) use ($a) {
return $b["drug_id"] === $a["drug_id"];
});
}

Answer 3

I do not recommended nested loops they will do too many unnecessary iterations. Instead, because the drug_ids in the first array are unique, copy them to be the first level's keys -- this will let you swiftly associate data between the two arrays. When the loop is done, you can remove the first level keys with array_values().
Code: (Demo)
$drugs = array_column($array1, null, 'drug_id');
foreach ($array2 as $row) {
if (isset($drugs[$row['drug_id']])) {
$drugs[$row['drug_id']]['decisions'][] = $row;
}
}
var_export(array_values($drugs));