How to group an array of associative arrays and declare custom keys? - php

Question

Can someone help me with converting a php array in a grouped format? I am trying to group them by id. I would like to have the following array converted:
$Arr1=Array
(
0 => Array
(
"id" => "4123",
"test_number" => "1",
"sat_total" => "1050"
),
1 => Array
(
"id" => "4123",
"test_number" => "2",
"sat_total" => "1130"
),
2 => Array
(
"id" => "4123",
"test_number" => "3",
"sat_total" => "1120"
),
3 => Array
(
"id" => "5555",
"test_number" => "1",
"sat_total" => "1130"
),
4 => Array
(
"id" => "5555",
"test_number" => "2",
"sat_total" => "1160"
)
);
into this:
$Arr2=Array
(
0 => Array
(
"id" => "4123",
"Score1" => "1050",
"Score2" => "1130",
"Score3" => "1120"
),
1 => Array
(
"id" => "5555",
"Score1" => "1130",
"Score2" => "1160"
)
);
I have tried a little bit, but can't seem to find how to make it work.

Answer 1

You only need to iterate your rows of data, determine if each row is the first occurring id value or not, then either declare the initial values, or add a variably keyed element to the group. When the loop finishes, call array_values() to reindex the array (remove the temporary keys).
Code: (Demo)
$Arr1=[
["id" => "4123", "test_number" => "1", "sat_total" => "1050"],
["id" => "4123", "test_number" => "2", "sat_total" => "1130"],
["id" => "4123", "test_number" => "3", "sat_total" => "1120"],
["id" => "5555", "test_number" => "1", "sat_total" => "1130"],
["id" => "5555", "test_number" => "2", "sat_total" => "1160"]
];
foreach ($Arr1 as $set) {
if (!isset($result[$set['id']])) {
$result[$set['id']] = ['id' => $set['id'], 'Score1' => $set['sat_total']];
} else {
$result[$set['id']]['Score' . sizeof($result[$set['id']])] = $set['sat_total'];
}
}
var_export(array_values($result));
Output:
array (
0 =>
array (
'id' => '4123',
'Score1' => '1050',
'Score2' => '1130',
'Score3' => '1120',
),
1 =>
array (
'id' => '5555',
'Score1' => '1130',
'Score2' => '1160',
),
)

Answer 2

This method will find the scores matching the $id.
It uses three array_intersects to match all the values correct.
This method will only loop the number of unique IDs, in your case two times.
Plus the times to create the score keys.
I do agree with what ggorlen says about the keys. That will also create a more efficient code.
$ids = array_column($Arr1, "id");
$sat = array_column($Arr1, "sat_total");
foreach(array_unique($ids) as $id){
$new[$id] = ["id" => $id];
$tmp = array_values(array_intersect_key($sat,array_intersect_key($Arr1, array_intersect($ids, [$id]))));
for($i=1;$i<=count($tmp);$i++) $new[$id]["Score" . $i] = $tmp[$i-1];
}
var_dump($new);
https://3v4l.org/ag3To
The output is an associative array with id as key.
You can use array_values if you want to make it indexed.
Just to show how much more efficient the code can be with one score array.
This is what it would look like:
$ids = array_column($Arr1, "id");
$sat = array_column($Arr1, "sat_total");
foreach(array_unique($ids) as $id){
$new[] = ["id" => $id, "scores" => array_values(array_intersect_key($sat,array_intersect_key($Arr1, array_intersect($ids, [$id]))))];
}
var_dump($new);
https://3v4l.org/mdA0W

Answer 3

$arr2 = [];
$i = 0;
$length = count($arr1);
do {
$builder = $arr1[$i];
// grab the first item from the original array
$builder = [
// set its initial properties
'id' => $arr1[$i]['id'],
'Score1' => $arr1[$i]['sat_total'],
];
// initialise the subsequent score number
$testNumber = 2;
// prepare to look ahead in the original array for a matching id
while (($i + 1) < $length) { // only look ahead if it is possible to
if ($arr1[$i + 1]['id'] == $builder['id']) {
// did you find a matching id? if so, let's set the subsequent score
$builder["Score$testNumber"] = $arr1[$i + 1]['sat_total'];
$testNumber++; // increase the next score number
$i++; // increase the original array index
} else {
// no luck? let's go forwards and set the next record
break;
}
}
$arr2[] = $builder; // set the built record into the new array
$i++; // move the pointer forwards
} while ($i < $length); // as long as there are items ahead
Not often you get to use a do-while. But it works :)
Feed it your original array $arr1 and $arr2 will be set.
It works by looking forward for matching ids. This solution assumes your original array is ordered by id! So unless you trust the input - don't use this solution!
Otherwise this is a simple, fast, and fairly readable solution to what looks to me like a school exercise?
If you want something that is safe, the other solutions here are suitable.

Answer 4

I'm not sure this structure is ideal--it seems like your keys "Score1", "Score2" etc would be best as an array like scores => [1050, 1130, ...] and it feels like the ids should be keys in the result array. But in any case, this gives your requested output:
$res = [];
foreach ($arr as $e) {
if (!array_key_exists($e['id'], $res)) {
$res[$e['id']] = [];
}
$res[$e['id']]["Score".(count($res[$e['id']])+1)] = $e['sat_total'];
}
$count = 0;
foreach ($res as $k => $v) {
$res[$k]['id'] = $k;
$res[$count++] = $res[$k];
unset($res[$k]);
}
print_r($res);
Output
Array
(
[0] => Array
(
[Score1] => 1050
[Score2] => 1130
[Score3] => 1120
[id] => 4123
)
[1] => Array
(
[Score1] => 1130
[Score2] => 1160
[id] => 5555
)
)
Note that I did two passes which is a little verbose, but taking the time to key in the data ids into the array in the first pass should improve a linear search through the array for each element into O(1) hashing, so I think it's worth the extra loop block.