From 39ab49fb2beb3261a03ff2749183a2fdf2dc7f6e Mon Sep 17 00:00:00 2001
From: Christian <christian1827@gmail.com>
Date: Fri, 27 Jan 2023 21:36:13 -0500
Subject: [PATCH] Exercise: Fix error in calculated score with "Global multiple
 answer" - refs BT#20518

---
 main/exercise/exercise.class.php | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/main/exercise/exercise.class.php b/main/exercise/exercise.class.php
index f164bd6238..5ac5316815 100755
--- a/main/exercise/exercise.class.php
+++ b/main/exercise/exercise.class.php
@@ -3900,6 +3900,16 @@ class Exercise
             $answerMatching[$real_answer['iid']] = $real_answer['answer'];
         }
 
+        // Get correct answers for multiple answers.
+        $sql = "SELECT iid
+                FROM $table_ans
+                WHERE question_id = $questionId AND correct = 1";
+        $resMAnswer = Database::query($sql);
+        $correctMultipleAnswers = [];
+        while ($rowMAanswer = Database::fetch_array($resMAnswer)) {
+            $correctMultipleAnswers[] = $rowMAanswer['iid'];
+        }
+
         // Get first answer needed for global question, no matter the answer shuffle option;
         $firstAnswer = [];
         if ($answerType == MULTIPLE_ANSWER_COMBINATION ||
@@ -4155,6 +4165,7 @@ class Exercise
                     $totalScore += $answerWeighting;
                     break;
                 case GLOBAL_MULTIPLE_ANSWER:
+                    $validAnswer = false;
                     if ($from_database) {
                         $choice = [];
                         $sql = "SELECT answer FROM $TBL_TRACK_ATTEMPT
@@ -4163,14 +4174,20 @@ class Exercise
                         while ($row = Database::fetch_array($resultans)) {
                             $choice[$row['answer']] = 1;
                         }
+                        if (!empty($choice) && count($choice) == count($correctMultipleAnswers)) {
+                            $validAnswer = (0 == count(array_diff(array_keys($choice), $correctMultipleAnswers)));
+                        }
                         $studentChoice = isset($choice[$answerAutoId]) ? $choice[$answerAutoId] : null;
                         $real_answers[$answerId] = (bool) $studentChoice;
-                        if ($studentChoice) {
+                        if ($studentChoice && $validAnswer) {
                             $questionScore += $answerWeighting;
                         }
                     } else {
+                        if (!empty($choice) && count($choice) == count($correctMultipleAnswers)) {
+                            $validAnswer = (0 == count(array_diff(array_keys($choice), $correctMultipleAnswers)));
+                        }
                         $studentChoice = isset($choice[$answerAutoId]) ? $choice[$answerAutoId] : null;
-                        if (isset($studentChoice)) {
+                        if (isset($studentChoice) && $validAnswer) {
                             $questionScore += $answerWeighting;
                         }
                         $real_answers[$answerId] = (bool) $studentChoice;