diff --git a/main/inc/ajax/exercise.ajax.php b/main/inc/ajax/exercise.ajax.php
index 776839626e..4632cab248 100755
--- a/main/inc/ajax/exercise.ajax.php
+++ b/main/inc/ajax/exercise.ajax.php
@@ -1,6 +1,8 @@
 <?php
 /* For licensing terms, see /license.txt */
 
+use \ChamiloSession as Session;
+
 /**
  * Responses to AJAX calls
  */
@@ -209,7 +211,7 @@ switch ($action) {
         break;
     case 'add_question_to_reminder':
         /** @var Exercise $objExercise */
-        $objExercise  = $_SESSION['objExercise'];
+        $objExercise = Session::read('objExercise');
         if (empty($objExercise)) {
             echo 0;
             exit;
@@ -257,11 +259,11 @@ switch ($action) {
 
             // Exercise information.
             /** @var Exercise $objExercise */
-            $objExercise = isset($_SESSION['objExercise']) ? $_SESSION['objExercise'] : null;
+            $objExercise = Session::read('objExercise');
 
             // Question info.
             $question_id = isset($_REQUEST['question_id']) ? intval($_REQUEST['question_id']) : null;
-            $question_list = $_SESSION['questionList'];
+            $question_list = Session::read('questionList');
 
             // If exercise or question is not set then exit.
             if (empty($question_list) || empty($objExercise)) {
diff --git a/main/inc/introductionSection.inc.php b/main/inc/introductionSection.inc.php
index d6c301c053..6e4a980dcd 100755
--- a/main/inc/introductionSection.inc.php
+++ b/main/inc/introductionSection.inc.php
@@ -245,12 +245,10 @@ if ($tool == TOOL_COURSE_HOMEPAGE && !isset($_GET['intro_cmdEdit'])) {
             $thematic_advance_info['start_date'],
             DATE_TIME_FORMAT_LONG
         );
-        $userInfo = $_SESSION['_user'];
+        $userInfo = api_get_user_info();
         $courseInfo = api_get_course_info();
         $titleThematic = $thematic_advance .' : '. $courseInfo['name'] . ' <b>( '. $thematicScore .' )</b>';
 
-
-
         $infoUser = '<div class="thematic-avatar"><img src="' . $userInfo['avatar'] . '" class="img-circle img-responsive"></div>';
         $infoUser .= '<div class="progress">
                         <div class="progress-bar progress-bar-danger" role="progressbar" style="width: ' . $thematicScore . ';">
@@ -258,7 +256,6 @@ if ($tool == TOOL_COURSE_HOMEPAGE && !isset($_GET['intro_cmdEdit'])) {
                         </div>
                     </div>';
 
-
         $thematicItemOne = '
         <div class="col-md-6 items-progress">
             <div class="thematic-cont '.$class1.'">
diff --git a/main/inc/lib/course_home.lib.php b/main/inc/lib/course_home.lib.php
index e7633a8886..8a0ebad784 100755
--- a/main/inc/lib/course_home.lib.php
+++ b/main/inc/lib/course_home.lib.php
@@ -153,9 +153,9 @@ class CourseHome
                 $cat == 'courseAdmin' || $cat == 'platformAdmin'
             ) {
                 if (strpos($tool['name'], 'visio_') !== false) {
-                    $cell_content .= '<a  href="javascript: void(0);" onclick="javascript: window.open(\''.$tool['link'].$link_annex.'\',\'window_visio'.$_SESSION['_cid'].'\',config=\'height=\'+730+\', width=\'+1020+\', left=2, top=2, toolbar=no, menubar=no, scrollbars=yes, resizable=yes, location=no, directories=no, status=no\')" target="'.$tool['target'].'"><img src="'.$tool['img'].'" title="'.$tool_name.'" alt="'.$tool_name.'" align="absmiddle" border="0">'.$tool_name.'</a>';
+                    $cell_content .= '<a  href="javascript: void(0);" onclick="javascript: window.open(\''.$tool['link'].$link_annex.'\',\'window_visio'.api_get_course_id().'\',config=\'height=\'+730+\', width=\'+1020+\', left=2, top=2, toolbar=no, menubar=no, scrollbars=yes, resizable=yes, location=no, directories=no, status=no\')" target="'.$tool['target'].'"><img src="'.$tool['img'].'" title="'.$tool_name.'" alt="'.$tool_name.'" align="absmiddle" border="0">'.$tool_name.'</a>';
                 } elseif (strpos($tool['name'], 'chat') !== false && api_get_course_setting('allow_open_chat_window')) {
-                    $cell_content .= '<a href="javascript: void(0);" onclick="javascript: window.open(\''.$tool['link'].$link_annex.'\',\'window_chat'.$_SESSION['_cid'].'\',config=\'height=\'+600+\', width=\'+825+\', left=2, top=2, toolbar=no, menubar=no, scrollbars=yes, resizable=yes, location=no, directories=no, status=no\')" target="'.$tool['target'].'"><img src="'.$tool['img'].'" title="'.$tool_name.'" alt="'.$tool_name.'" align="absmiddle" border="0">'.$tool_name.'</a>';
+                    $cell_content .= '<a href="javascript: void(0);" onclick="javascript: window.open(\''.$tool['link'].$link_annex.'\',\'window_chat'.api_get_course_id().'\',config=\'height=\'+600+\', width=\'+825+\', left=2, top=2, toolbar=no, menubar=no, scrollbars=yes, resizable=yes, location=no, directories=no, status=no\')" target="'.$tool['target'].'"><img src="'.$tool['img'].'" title="'.$tool_name.'" alt="'.$tool_name.'" align="absmiddle" border="0">'.$tool_name.'</a>';
                     // don't replace img with display::return_icon because $tool['img'] = api_get_path(WEB_IMG_PATH).$tool['img']
                 } else {
                     $cell_content .= '<a href="'.$tool['link'].$link_annex.'" target="'.$tool['target'].'"><img src="'.$tool['img'].'" title="'.$tool_name.'" alt="'.$tool_name.'" align="absmiddle" border="0">'.$tool_name.'</a>';
@@ -165,9 +165,9 @@ class CourseHome
                 // INVISIBLE
                 if (api_is_allowed_to_edit(null, true)) {
                     if (strpos($tool['name'], 'visio_') !== false) {
-                        $cell_content .= '<a  href="javascript: void(0);" onclick="window.open(\''.$tool['link'].$link_annex.'\',\'window_visio'.$_SESSION['_cid'].'\',config=\'height=\'+730+\', width=\'+1020+\', left=2, top=2, toolbar=no, menubar=no, scrollbars=yes, resizable=yes, location=no, directories=no, status=no\')" target="'.$tool['target'].'"><img src="'.str_replace(".gif", "_na.gif", $tool['img']).'" title="'.$tool_name.'" alt="'.$tool_name.'" align="absmiddle" border="0">'.$tool_name.'</a>';
+                        $cell_content .= '<a  href="javascript: void(0);" onclick="window.open(\''.$tool['link'].$link_annex.'\',\'window_visio'.api_get_course_id().'\',config=\'height=\'+730+\', width=\'+1020+\', left=2, top=2, toolbar=no, menubar=no, scrollbars=yes, resizable=yes, location=no, directories=no, status=no\')" target="'.$tool['target'].'"><img src="'.str_replace(".gif", "_na.gif", $tool['img']).'" title="'.$tool_name.'" alt="'.$tool_name.'" align="absmiddle" border="0">'.$tool_name.'</a>';
                     } elseif (strpos($tool['name'], 'chat') !== false && api_get_course_setting('allow_open_chat_window')) {
-                        $cell_content .= '<a href="javascript: void(0);" onclick="javascript: window.open(\''.$tool['link'].$link_annex.'\',\'window_chat'.$_SESSION['_cid'].'\',config=\'height=\'+600+\', width=\'+825+\', left=2, top=2, toolbar=no, menubar=no, scrollbars=yes, resizable=yes, location=no, directories=no, status=no\')" target="'.$tool['target'].'" class="invisible"><img src="'.str_replace(".gif", "_na.gif", $tool['img']).'" title="'.$tool_name.'" alt="'.$tool_name.'" align="absmiddle" border="0">'.$tool_name.'</a>';
+                        $cell_content .= '<a href="javascript: void(0);" onclick="javascript: window.open(\''.$tool['link'].$link_annex.'\',\'window_chat'.api_get_course_id().'\',config=\'height=\'+600+\', width=\'+825+\', left=2, top=2, toolbar=no, menubar=no, scrollbars=yes, resizable=yes, location=no, directories=no, status=no\')" target="'.$tool['target'].'" class="invisible"><img src="'.str_replace(".gif", "_na.gif", $tool['img']).'" title="'.$tool_name.'" alt="'.$tool_name.'" align="absmiddle" border="0">'.$tool_name.'</a>';
                         // don't replace img with display::return_icon because $tool['img'] = api_get_path(WEB_IMG_PATH).$tool['img']
                     } else {
                         $cell_content .= '<a href="'.$tool['link'].$link_annex.'" target="'.$tool['target'].'" class="invisible">
@@ -342,9 +342,9 @@ class CourseHome
                 $html .= '<td width="50%" height="30">';
 
                 if (strpos($tool['name'], 'visio_') !== false) {
-                    $html .= '<a  '.$class.' href="javascript: void(0);" onclick="javascript: window.open(\''.htmlspecialchars($tool['link']).(($tool['image'] == 'external.gif' || $tool['image'] == 'external_na.gif') ? '' : $qm_or_amp.api_get_cidreq()).'\',\'window_visio'.$_SESSION['_cid'].'\',config=\'height=\'+730+\', width=\'+1020+\', left=2, top=2, toolbar=no, menubar=no, scrollbars=yes, resizable=yes, location=no, directories=no, status=no\')" target="'.$tool['target'].'">';
+                    $html .= '<a  '.$class.' href="javascript: void(0);" onclick="javascript: window.open(\''.htmlspecialchars($tool['link']).(($tool['image'] == 'external.gif' || $tool['image'] == 'external_na.gif') ? '' : $qm_or_amp.api_get_cidreq()).'\',\'window_visio'.api_get_course_id().'\',config=\'height=\'+730+\', width=\'+1020+\', left=2, top=2, toolbar=no, menubar=no, scrollbars=yes, resizable=yes, location=no, directories=no, status=no\')" target="'.$tool['target'].'">';
                 } elseif (strpos($tool['name'], 'chat') !== false && api_get_course_setting('allow_open_chat_window')) {
-                    $html .= '<a href="javascript: void(0);" onclick="javascript: window.open(\''.htmlspecialchars($tool['link']).$qm_or_amp.api_get_cidreq().'\',\'window_chat'.$_SESSION['_cid'].'\',config=\'height=\'+600+\', width=\'+825+\', left=2, top=2, toolbar=no, menubar=no, scrollbars=yes, resizable=yes, location=no, directories=no, status=no\')" target="'.$tool['target'].'"'.$class.'>';
+                    $html .= '<a href="javascript: void(0);" onclick="javascript: window.open(\''.htmlspecialchars($tool['link']).$qm_or_amp.api_get_cidreq().'\',\'window_chat'.api_get_course_id().'\',config=\'height=\'+600+\', width=\'+825+\', left=2, top=2, toolbar=no, menubar=no, scrollbars=yes, resizable=yes, location=no, directories=no, status=no\')" target="'.$tool['target'].'"'.$class.'>';
                 } else {
                     $html .= '<a href="'.htmlspecialchars($tool['link']).(($tool['image'] == 'external.gif' || $tool['image'] == 'external_na.gif') ? '' : $qm_or_amp.api_get_cidreq()).'" target="'.$tool['target'].'" '.$class.'>';
                 }
@@ -413,7 +413,7 @@ class CourseHome
                     $html .= '<div class="btn-options">';
                     $html .= '<div class="btn-group btn-group-sm" role="group">';
                     foreach ($lnk as & $this_link) {
-                        if (!$tool['adminlink']) { 
+                        if (!$tool['adminlink']) {
                             $html .= '<a class="btn btn-default" title='.$this_link['title'].' href="'.api_get_self().'?'.api_get_cidreq().'&amp;id='.$tool['id'].'&amp;'.$this_link['cmd'].'">'.$this_link['name'].'</a>';
                         }
                     }
@@ -828,7 +828,7 @@ class CourseHome
                         'id' => 'tooldesc_'.$toolId,
                         'href' => '"javascript: void(0);"',
                         'class' => $class,
-                        'onclick' => 'javascript: window.open(\''.$tool['link'].'\',\'window_visio'.$_SESSION['_cid'].'\',config=\'height=\'+730+\', width=\'+1020+\', left=2, top=2, toolbar=no, menubar=no, scrollbars=yes, resizable=yes, location=no, directories=no, status=no\')',
+                        'onclick' => 'javascript: window.open(\''.$tool['link'].'\',\'window_visio'.api_get_course_id().'\',config=\'height=\'+730+\', width=\'+1020+\', left=2, top=2, toolbar=no, menubar=no, scrollbars=yes, resizable=yes, location=no, directories=no, status=no\')',
                         'target' => $tool['target']
                     );
                 } elseif (strpos($tool['name'], 'chat') !== false && api_get_course_setting('allow_open_chat_window')) {
@@ -836,7 +836,7 @@ class CourseHome
                         'id' => 'tooldesc_'.$toolId,
                         'class' => $class,
                         'href' => 'javascript: void(0);',
-                        'onclick' => 'javascript: window.open(\''.$tool['link'].'\',\'window_chat'.$_SESSION['_cid'].'\',config=\'height=\'+600+\', width=\'+825+\', left=2, top=2, toolbar=no, menubar=no, scrollbars=yes, resizable=yes, location=no, directories=no, status=no\')', //Chat Open Windows
+                        'onclick' => 'javascript: window.open(\''.$tool['link'].'\',\'window_chat'.api_get_course_id().'\',config=\'height=\'+600+\', width=\'+825+\', left=2, top=2, toolbar=no, menubar=no, scrollbars=yes, resizable=yes, location=no, directories=no, status=no\')', //Chat Open Windows
                         'target' => $tool['target']
                     );
                 } else {
@@ -1203,7 +1203,7 @@ class CourseHome
                 if (strpos($navigation_item['link'], 'chat') !== false &&
                     api_get_course_setting('allow_open_chat_window', $course_id)
                 ) {
-                    $html .= '<a class="btn btn-default text-left" href="javascript: void(0);" onclick="javascript: window.open(\''.$navigation_item['link'].'\',\'window_chat'.$_SESSION['_cid'].'\',config=\'height=\'+600+\', width=\'+825+\', left=2, top=2, toolbar=no, menubar=no, scrollbars=yes, resizable=yes, location=no, directories=no, status=no\')" target="'.$navigation_item['target'].'"';
+                    $html .= '<a class="btn btn-default text-left" href="javascript: void(0);" onclick="javascript: window.open(\''.$navigation_item['link'].'\',\'window_chat'.api_get_course_id().'\',config=\'height=\'+600+\', width=\'+825+\', left=2, top=2, toolbar=no, menubar=no, scrollbars=yes, resizable=yes, location=no, directories=no, status=no\')" target="'.$navigation_item['target'].'"';
                 } else {
                     $html .= '<a class="btn btn-default text-left" href="'.$navigation_item['link'].'" target="_top" ';
                 }
@@ -1226,7 +1226,6 @@ class CourseHome
             $html .= '</ul>';
         }
         $html .= '</div>';
-        
 
         return $html;
     }
@@ -1249,7 +1248,7 @@ class CourseHome
                 if (strpos($navigation_item['link'], 'chat') !== false &&
                     api_get_course_setting('allow_open_chat_window')
                 ) {
-                    $html .= '<a class="items-icon" href="javascript: void(0);" onclick="javascript: window.open(\''.$navigation_item['link'].'\',\'window_chat'.$_SESSION['_cid'].'\',config=\'height=\'+600+\', width=\'+825+\', left=2, top=2, toolbar=no, menubar=no, scrollbars=yes, resizable=yes, location=no, directories=no, status=no\')" target="'.$navigation_item['target'].'"';
+                    $html .= '<a class="items-icon" href="javascript: void(0);" onclick="javascript: window.open(\''.$navigation_item['link'].'\',\'window_chat'.api_get_course_id().'\',config=\'height=\'+600+\', width=\'+825+\', left=2, top=2, toolbar=no, menubar=no, scrollbars=yes, resizable=yes, location=no, directories=no, status=no\')" target="'.$navigation_item['target'].'"';
                 } else {
                     $html .= '<a class="items-icon" href="'.$navigation_item['link'].'"';
                 }
diff --git a/main/survey/survey_list.php b/main/survey/survey_list.php
index 4f0c3c8718..c36c29e37d 100755
--- a/main/survey/survey_list.php
+++ b/main/survey/survey_list.php
@@ -90,11 +90,13 @@ if (isset($_GET['search']) && $_GET['search'] == 'advanced') {
     SurveyUtil::display_survey_search_form();
 }
 
+$sessionId = api_get_session_id();
+
 // Action handling: deleting a survey
-if ($action == 'delete' && isset($_GET['survey_id'])) {
+if ($action === 'delete' && isset($_GET['survey_id'])) {
     // Getting the information of the survey (used for when the survey is shared)
     $survey_data = SurveyManager::get_survey($_GET['survey_id']);
-    if (api_is_course_coach() && intval($_SESSION['id_session']) != $survey_data['session_id']) {
+    if (api_is_course_coach() && $sessionId != $survey_data['session_id']) {
         // The coach can't delete a survey not belonging to his session
         api_not_allowed();
         exit;