diff --git a/main/survey/surveyUtil.class.php b/main/survey/surveyUtil.class.php
index e03ade5869..1b14bd327e 100755
--- a/main/survey/surveyUtil.class.php
+++ b/main/survey/surveyUtil.class.php
@@ -480,16 +480,18 @@ class SurveyUtil
                 }
 
                 $ch_type = 'ch_'.$question['type'];
-                /** @var survey_question $display */
-                $display = new $ch_type();
-
-                $url = api_get_self();
-                $form = new FormValidator('question', 'post', $url);
-                $form->addHtml('<div class="survey_question_wrapper"><div class="survey_question">');
-                $form->addHtml($question['survey_question']);
-                $display->render($form, $question, $finalAnswer);
-                $form->addHtml('</div></div>');
-                $form->display();
+                if (class_exists($ch_type)) {
+                    /** @var survey_question $display */
+                    $display = new $ch_type();
+
+                    $url = api_get_self();
+                    $form = new FormValidator('question', 'post', $url);
+                    $form->addHtml('<div class="survey_question_wrapper"><div class="survey_question">');
+                    $form->addHtml($question['survey_question']);
+                    $display->render($form, $question, $finalAnswer);
+                    $form->addHtml('</div></div>');
+                    $form->display();
+                }
             }
         }
     }
diff --git a/main/survey/survey_invitation.php b/main/survey/survey_invitation.php
index 150d4b006b..be2a50f663 100755
--- a/main/survey/survey_invitation.php
+++ b/main/survey/survey_invitation.php
@@ -63,24 +63,25 @@ if ($survey_data['anonymous'] == 1) {
     );
     $answered_data = [];
 }
+$url = api_get_self().'?survey_id='.$survey_id.'&'.api_get_cidreq();
 
 if (!isset($_GET['view']) || $_GET['view'] == 'invited') {
     echo get_lang('ViewInvited').' | ';
 } else {
-    echo '	<a href="'.api_get_self().'?survey_id='.$survey_id.'&view=invited">'.
+    echo '	<a href="'.$url.'&view=invited">'.
         get_lang('ViewInvited').'</a> |';
 }
 if ($_GET['view'] == 'answered') {
     echo get_lang('ViewAnswered').' | ';
 } else {
-    echo '	<a href="'.api_get_self().'?survey_id='.$survey_id.'&view=answered">'.
+    echo '	<a href="'.$url.'&view=answered">'.
         get_lang('ViewAnswered').'</a> |';
 }
 
 if ($_GET['view'] == 'unanswered') {
     echo get_lang('ViewUnanswered');
 } else {
-    echo '	<a href="'.api_get_self().'?survey_id='.$survey_id.'&view=unanswered">'.
+    echo '	<a href="'.$url.'&view=unanswered">'.
         get_lang('ViewUnanswered').'</a>';
 }
 
@@ -118,11 +119,13 @@ while ($row = Database::fetch_assoc($res)) {
         } else {
             echo '<td>'.$row['user'].'</td>';
         }
-        echo '	<td>'.api_get_local_time($row['invitation_date']).'</td>';
+        echo '	<td>'.Display::dateToStringAgoAndLongDate($row['invitation_date']).'</td>';
         echo '	<td>';
 
         if (in_array($row['user'], $answered_data) && !api_get_configuration_value('hide_survey_reporting_button')) {
-            echo '<a href="'.api_get_path(WEB_CODE_PATH).'survey/reporting.php?action=userreport&survey_id='.$survey_id.'&user='.$row['user'].'">'.
+            echo '<a href="'.
+                api_get_path(WEB_CODE_PATH).
+                'survey/reporting.php?action=userreport&survey_id='.$survey_id.'&user='.$row['user'].'&'.api_get_cidreq().'">'.
                 get_lang('ViewAnswers').'</a>';
         } else {
             echo '-';
@@ -136,5 +139,4 @@ while ($row = Database::fetch_assoc($res)) {
 // Closing the table
 echo '</table>';
 
-// Footer
 Display::display_footer();
diff --git a/main/survey/survey_invite.php b/main/survey/survey_invite.php
index d9dd60d2e0..e7cbb3356c 100755
--- a/main/survey/survey_invite.php
+++ b/main/survey/survey_invite.php
@@ -237,11 +237,12 @@ if ($form->validate()) {
     // Counting the number of people that are invited
     $total_invited = SurveyUtil::update_count_invited($survey_data['code']);
     $total_count = $count_course_users + $counter_additional_users;
+    $invitationUrl = api_get_path(WEB_CODE_PATH).'survey/survey_invitation.php?survey_id='.$survey_data['survey_id'].'&'.api_get_cidreq();
     if ($total_invited > 0) {
-        $message = '<a href="'.api_get_path(WEB_CODE_PATH).'survey/survey_invitation.php?view=answered&survey_id='.$survey_data['survey_id'].'">'.
+        $message = '<a href="'.$invitationUrl.'&view=answered">'.
             $survey_data['answered'].'</a> ';
         $message .= get_lang('HaveAnswered').' ';
-        $message .= '<a href="'.api_get_path(WEB_CODE_PATH).'survey/survey_invitation.php?view=invited&survey_id='.$survey_data['survey_id'].'">'.
+        $message .= '<a href="'.$invitationUrl.'&view=invited">'.
             $total_invited.'</a> ';
         $message .= get_lang('WereInvited');
         echo Display::return_message($message, 'normal', false);