Alphabetizing multidimensional array with SQL or PHP - php

Question

I'm working on programming a gradebook, and I've ran into a bit of an issue I'm trying to figure out how to approach.
I have three tables which are at play in this script: (1) the "assignments" table which contains info about each assignment, (2) the "assignGrades" table which contains student scores on assignments (3) the "students" table which contains student information.
Now, the problem is coming whenever I add a new student to the class. Logically, if a student joins a class mid-semester, they would not be assigned "past work" from earlier in the year. With this in mind, there would be no "connection" for an INNER JOIN statement. I have already tried using "LEFT JOIN" and "RIGHT JOIN" in this instance, but I am not having any luck.
Whenever I go to build a PHP array with the SQL statement below, I am running into a problem. If a student was added mid year, they are not properly alphabetizing into the array, which comes from the SELECT statement and the way this is organized. See the example below for student "Amy Appleton" which was added mid year, and is not in proper alphabetical order.
HOW I NEED HELP / DESIRED END RESULT:
I am trying to determine how to alphabetize my $array to be organized in order of last name. I have determined I will either accomplish this through rewriting my SQL statement or through using some sort of PHP usort, although I would much rather organize data on the SQL side if possible. My best guess would be to accomplish this through a LEFT JOIN, but I have tried every variation possible within my SQL statement and have not gotten any desired results.
SQL statement used:
SELECT students.firstName, students.lastName, assignments.assID, assignments.assEmoji, assignments.points, assignments.title, assignments.assigned, assignments.due, assignGrades.*
FROM students
LEFT JOIN assignGrades ON students.usid = assignGrades.usid
LEFT JOIN assignments ON assignGrades.assID = assignments.assID
WHERE subID=? OR subID IS NULL ORDER BY due, lastName, firstName
Snipet from PHP that is building the $array
while ($row = mysqli_fetch_assoc($results)) {
$array['assignments'][$row['assID']]['assEmoji'] = $row['assEmoji'];
$array['assignments'][$row['assID']]['title'] = $row['title'];
$array['assignments'][$row['assID']]['points'] = $row['points'];
$array['assignments'][$row['assID']]['assigned'] = $row['assigned'];
$array['assignments'][$row['assID']]['due'] = $row['due'];
$array['students'][$row['usid']]['firstName'] = $row['firstName'];
$array['students'][$row['usid']]['lastName'] = $row['lastName'];
$array['students'][$row['usid']]['fullName'] = $row['firstName']." ". $row['lastName'];
if ($row['status'] == 'graded' || $row['status'] == 'missing') {
$array['students'][$row['usid']]['earned'] = $array['students'][$row['usid']]['earned'] + $row['score'];
$array['students'][$row['usid']]['maxpts'] = $array['students'][$row['usid']]['maxpts'] + $row['points'];
}
$array['students'][$row['usid']]['submissions'][$row['assID']]['workID'] = $row['workID'];
$array['students'][$row['usid']]['submissions'][$row['assID']]['status'] = $row['status'];
if (isset($row['submitted'])) {$array['students'][$row['usid']]['submissions'][$row['assID']]['submitted'] = $row['submitted'];}
if (isset($row['method'])) {$array['students'][$row['usid']]['submissions'][$row['assID']]['method'] = $row['method'];}
if (isset($row['score'])) {$array['students'][$row['usid']]['submissions'][$row['assID']]['score'] = $row['score'];}
if (isset($row['score'])) {$array['students'][$row['usid']]['submissions'][$row['assID']]['points'] = $row['points'];}
if (isset($row['graded'])) {$array['students'][$row['usid']]['submissions'][$row['assID']]['graded'] = $row['graded'];}
if (isset($row['method'])) {$array['students'][$row['usid']]['submissions'][$row['assID']]['method'] = $row['method'];}
}
return $array;
Example print_r($array) from the SQL statement (Amy Appleton should appear on the top of $array['students'] since she is alphabetically before the other two students. However, since there is no entry on the assignGrades table for assignment #9 for her, she appears at the bottom)
Array
(
[assignments] => Array
(
[9] => Array
(
[assEmoji] => ✏️
[title] => Beginning of Year Activities
[points] => 10
[assigned] => 2021-08-16
[due] => 2021-08-20 15:00:00
)
[10] => Array
(
[assEmoji] => ✏️
[title] => Mid Year Project
[points] => 10
[assigned] => 2021-09-23
[due] => 2021-09-30 15:00:00
)
)
[students] => Array
(
[11] => Array
(
[firstName] => Zeke
[lastName] => Lee
[fullName] => Zeke Lee
[earned] => 103
[maxpts] => 120
[submissions] => Array
(
[9] => Array
(
[workID] => 539
[status] => graded
[submitted] => 2021-08-17 08:15:48
[method] => wall
[score] => 9
[points] => 10
[graded] => 2021-09-22 10:26:54
)
[10] => Array
(
[workID] => 541
[status] => graded
[submitted] => 2021-09-23 08:15:48
[method] => wall
[score] => 9
[points] => 10
[graded] => 2021-09-23 10:26:54
)
)
)
[12] => Array
(
[firstName] => John
[lastName] => Smith
[fullName] => John Smith
[earned] => 91
[maxpts] => 110
[submissions] => Array
(
[9] => Array
(
[workID] => 540
[status] => graded
[submitted] => 2021-08-17 08:45:48
[method] => wall
[score] => 7
[points] => 10
[graded] => 2021-09-22 10:28:54
)
[10] => Array
(
[workID] => 590
[status] => graded
[submitted] => 2021-09-23 09:15:48
[method] => wall
[score] => 9
[points] => 10
[graded] => 2021-09-23 11:24:54
)
)
)
[13] => Array
(
[firstName] => Amy
[lastName] => Appleton
[fullName] => Amy Appleton
[earned] => 91
[maxpts] => 110
[submissions] => Array
(
[10] => Array
(
[workID] => 913
[status] => graded
[submitted] => 2021-09-23 10:45:48
[method] => wall
[score] => 7
[points] => 10
[graded] => 2021-09-23 12:31:54
)
)
)
)
)
Array structure:
$array['assignments'][assID][details]
$array['students'][usid][details]
$array['students'][usid]['submissions'][assID][details]
Screenshots of table structure from SQL
Screenshot of CSV dump from SQL query

Answer 1

The main issue I see is that your query is trying to do too much. It is trying to get assignments in a specific order (by due), as well as students and their submissions in a different order (by lastName, firstName). For this reason, I would break this up into 2 separate queries. You can combine the datasets later to make your final data structure.
retrieve the assignments and order them by due date. This is a very simple query and the result set can be used directly.
retrieve all students and their submissions, if they exist, and order them by lastName, first name. Then, in PHP, manipulate the dataset into the format you need.
Pseudocode
// Get assignments. These can be used directly in your data structure `$combined`.
//
// Order by due date
$assignments = SELECT ... FROM assignments
WHERE ...
ORDER BY due;
// Get students and their assignments. These need to be manipulated to fit your
// requirements. Use a left join here because a student may not have started
// an assignment yet.
//
// Order by lastName, firstName
$students = SELECT ... FROM students a
LEFT JOIN assignGrades b ON b.usid = a.usid
ORDER BY lastName, firstName;
// See http://sandbox.onlinephpfunctions.com/code/9460c51954f8ea00f7ba75adadfcbf91fc03076e
// Loop over the student/submission dataset and manipulate it.
$studentMapping = [];
foreach($students as $row) {
// Build up student data if it doesn't already exist.
// Importantly, create an empty submissions element. If the student's
// submission doesn't exist, this is what will be returned.
$student = $studentMapping[$row['usid']] ?? [];
if (empty($student)) {
$student = [
'firstName' => $row['lastName'],
'lastName' => $row['lastName'],
...
'submissions' => [],
];
}
// Build up submissions data for the student if they have submitted an assignment.
// If they haven't submitted an assignment yet, their submissions array will remain empty.
if (!empty($row['assignment_id'])) {
$student['submissions'][] = [
'assignmentId' => $row['assignment_id'],
'status' => $row['status'],
...
];
}
// Finally, assign the student (and their submissions) to the $studentMapping array.
$studentMapping[$row['usid']] = $student;
}
// Now combine them into your final datastructure.
$combined = [
'assignments' => $assignments,
'students' => $studentMapping,
];