force integer comparison for mc_exercise, fixes #259

exercises/mc_exercise.php

@@ -108,10 +108,10 @@ class mc_exercise extends Exercise
         $response = $solution->response;
 
         foreach ($this->task['answers'] as $i => $answer) {
-            if ($response[$i] == '-1') {
+            if (!isset($response[$i])) {
                 $points = null;
             } else {
-                $points = $response[$i] == $answer['score'] ? 1 : 0;
+                $points = (int) $response[$i] == $answer['score'] ? 1 : 0;
             }
 
             $result[] = ['points' => $points, 'safe' => true];

views/exercises/mc_exercise/correct.php

@@ -9,8 +9,8 @@
 
             <?= formatReady($entry['text']) ?>
 
-            <? if ($solution->id): ?>
-                <? if ($response[$key] == $entry['score']): ?>
+            <? if (isset($response[$key])): ?>
+                <? if ((int) $response[$key] == $entry['score']): ?>
                     <?= Icon::create('accept', 'status-green', ['class' => 'correction_marker', 'title' => _vips('richtig')]) ?>
                 <? else: ?>
                     <?= Icon::create('decline', 'status-red', ['class' => 'correction_marker', 'title' => _vips('falsch')]) ?>

views/exercises/mc_exercise/print.php

@@ -9,8 +9,8 @@
 
             <?= formatReady($entry['text']) ?>
 
-            <? if ($solution->id && $print_correction): ?>
-                <? if ($response[$key] == $entry['score']): ?>
+            <? if (isset($response[$key]) && $print_correction): ?>
+                <? if ((int) $response[$key] == $entry['score']): ?>
                     <?= Icon::create('accept', 'status-green', ['class' => 'correction_marker', 'title' => _vips('richtig')]) ?>
                 <? else: ?>
                     <?= Icon::create('decline', 'status-red', ['class' => 'correction_marker', 'title' => _vips('falsch')]) ?>