How to group and sum subarray items in PHP Laravel - php

Question

I have N arrays. with n grade_items subarrays.
just like this.
array:2 [
0 => array:10 [
"id" => 9
"course_id" => 6
"semester_id" => 2
"name" => "Assignment"
"total_score" => 10
"grade_items" => array:1 [
0 => array:7 [
"id" => 5
"gradelist_id" => 9
"student_course_id" => 11
"score" => 8
"created_at" => "2020-04-21T03:31:20.000000Z"
"updated_at" => "2020-04-21T20:04:10.000000Z"
]
]
]
1 => array:10 [
"id" => 10
"course_id" => 6
"semester_id" => 2
"name" => "Pop Quiz"
"total_score" => 20
"grade_items" => array:1 [
0 => array:7 [
"id" => 6
"gradelist_id" => 10
"student_course_id" => 11
"score" => null
"created_at" => "2020-04-22T00:11:17.000000Z"
"updated_at" => "2020-04-22T00:11:17.000000Z"
]
]
]
]
I am trying to add each grade_item subarray from each array where the student_course_id is the same. Where there is only one grade_item and no other one with the same student_course_id, then it returns just that one value instead of a sum.
I have gone through this thread
But it just messed up the logic in my head further. I've been at this for weeks.
When I add the scores from each grade_item, i want to put that value into another model say "result_model" that would look like:
result_item [
"id" => 1,
"student_course_id" => 11,
"score" => 15 //total of grade_items from all arrays where the student_course_id's were the same
];
Help!

Answer 1

So basically you want to regroup the current information to receive the sum of grades. It seems the the information comes form a databases, so why don't you GROUP BY and sum on database level?
Anyway. Here's an approach. Start by keeping a map of student_course_id => score. First it will be empty: $map = [];
Then start iterating through the whole structure e.g. foreach ($data as $row. For each row, you need to check all the corresponding grade_items e.g. foreach ($row['grade_items'] as $gradeItem). Now you need to check whether the student_course_id from the grade item is present into the mapping.
If it's not present, create it with starting value of zero e.g.
if (!key_exists($gradeItem['student_course_id'], $map)) {
$map[$gradeItem['student_course_id']] = 0;
}
Once you ensure that the student_course_id is present, you can just add to the previous value the current score => $map[$gradeItem['student_course_id']] += $gradeItem['score'].

Answer 2

Here is a sample data i used
$array = [
[
'id' => 9,
'course_id' => 6,
'semester_id' => 2,
'name' => 'Assignment',
'total_score' => 10,
'grade_items' => [
[
'id' => 5,
'gradelist_id' => 9,
'student_course_id' => 11,
'score' => 8,
'created_at' => '2020-04-21T03:31:20.000000Z',
'updated_at' => '2020-04-21T20:04:10.000000Z',
],
[
'id' => 5,
'gradelist_id' => 9,
'student_course_id' => 15,
'score' => 15,
'created_at' => '2020-04-21T03:31:20.000000Z',
'updated_at' => '2020-04-21T20:04:10.000000Z',
]
]
],
[
'id' => 10,
'course_id' => 6,
'semester_id' => 2,
'name' => 'Pop Quiz',
'total_score' => 20,
'grade_items' => [
[
'id' => 6,
'gradelist_id' => 10,
'student_course_id' => 11,
'score' => 21,
'created_at' => '2020-04-22T00:11:17.000000Z',
'updated_at' => '2020-04-22T00:11:17.000000Z',
],
[
'id' => 6,
'gradelist_id' => 10,
'student_course_id' => 23,
'score' => 15,
'created_at' => '2020-04-22T00:11:17.000000Z',
'updated_at' => '2020-04-22T00:11:17.000000Z',
]
]
]
];
and here is the code;
$id = 0;
return collect($array)
->flatMap(function ($item){
return $item['grade_items'];
})
->groupBy('student_course_id')
->transform(function ($subItems, $courseId) use (&$id) {
$id++;
return [
'id' => $id,
'student_course_id' => $courseId,
'score' => $subItems->sum('score')
];
})
->values()
->toArray();
here is the result;
[
[
'id' => 1,
'student_course_id' => 11,
'score' => 29,
],
[
'id' => 2,
'student_course_id' => 15,
'score' => 15,
],
[
'id' => 3,
'student_course_id' => 23,
'score' => 15,
]
]

Answer 3

Use the sum() function. You can loop through the array, and do any checks you need, like if it is not Null etc, and pluck() it and then sum() it.

Answer 4

May I suggest recursivity approach?
<?php
function rec_sum_grades(&$array_grades, &$sum = 0){
$sum += $array_grades['total_score'];
if(!empty($array_grades['grade_items'])){
$this->rec_sum_grades($array_grades['grade_items'], $sum);
}
}
rec_sum_grades($array_grades, $sum);
echo $sum;
?>