Detect when id retrieved from php query is changed - php

Question

I'm running a query where I'm getting the average score of a student, by getting the average score of an activity type(quiz,exams,etc.) and multiplying it to its assigned grade percentage(ex: 80 *.03).
I've grouped the result by its activity_ID and Student ID.
To get the Grade of the student I need to add the score of each activity type. by simple adding all the result of each activity type.
(ex:grade =10.40+30+12;)
Now my problem is when the student ID is changed the result of the previous student is added to the result of the new one.
(ex:new student grade = previous result, plus his own)
I want to detect when the Student ID is changed inside the
while($row = mysqli_fetch_array($result)) {
$studentID_link = $row['studentID'];
$atName = $row['AT_name'];
$GLOBALS['AR_Score'] = $row['AVG(AR.Score)'];
$AT_gradePercentage =$row['AT_gradePercentage'];
$AT_gradePercentage /=100;
$periodGrades = $AR_Score*$AT_gradePercentage;
$variableName = $variableName + $periodGrades;
}

Answer 1

Use
mysqli_fetch_assoc()
Check for the id after storing the initial student id in a temp variable outside of the loop. Compare each new row's student ID to the previously stored temporary id. Also declare an array outside of the loop and use
array_push()
to push each total onto the array. Use an associative array with the student ID as the key and avoid using array_push if you are accessing student IDs out of order or use an index in mysql to allieviate this issue.
Honestly, you may want to reexamine your sql or show us if you want us to rewrite the code for you.
Update:
If the current mysqli_fetch_array is fetching an associative array, you can leave it, however refer to my above suggestions if you are having issues with that.
$curr_student = NULL;
$array = [];
while($row = mysqli_fetch_array($result)) {
$studentID_link = $row['studentID'];
if($curr_student === NULL || $curr_student !== $studentID_link){
$curr_student = $studentID_link;
if(!array_key_exists($curr_student, $array)) $array[$curr_student] = 0;
}
$atName = $row['AT_name'];
$GLOBALS['AR_Score'] = $row['AVG(AR.Score)'];
$AT_gradePercentage =$row['AT_gradePercentage'];
$AT_gradePercentage /=100;
$periodGrades = $AR_Score*$AT_gradePercentage;
$array[$curr_student] = $array[$curr_student] + $periodGrades;
}
I'm not certain about your global array and how you are using it, but this should work to add your students into each array member regardless of random access of student ID.