diff --git a/main/admin/course_list.php b/main/admin/course_list.php
index c454bf1fe4..4883c0d818 100755
--- a/main/admin/course_list.php
+++ b/main/admin/course_list.php
@@ -41,6 +41,13 @@ function get_course_data($from, $number_of_items, $column, $direction, $dataFunc
 {
     $addTeacherColumn = api_get_configuration_value('add_teachers_in_course_list');
     $table = Database::get_main_table(TABLE_MAIN_COURSE);
+    $from = (int) $from;
+    $number_of_items = (int) $number_of_items;
+    $column = (int) $column;
+
+    if (!in_array(strtolower($direction), ['asc', 'desc'])) {
+        $direction = 'desc';
+    }
 
     $teachers = '';
     if ($addTeacherColumn) {
@@ -250,6 +257,14 @@ function get_course_data_by_session($from, $number_of_items, $column, $direction
     $session_rel_course = Database::get_main_table(TABLE_MAIN_SESSION_COURSE);
     $session = Database::get_main_table(TABLE_MAIN_SESSION);
 
+    $from = (int) $from;
+    $number_of_items = (int) $number_of_items;
+    $column = (int) $column;
+
+    if (!in_array(strtolower($direction), ['asc', 'desc'])) {
+        $direction = 'desc';
+    }
+
     $sql = "SELECT
                 c.code AS col0,
                 c.title AS col1,
diff --git a/main/admin/course_list_admin.php b/main/admin/course_list_admin.php
index c22cf8a9b0..9ca041610d 100644
--- a/main/admin/course_list_admin.php
+++ b/main/admin/course_list_admin.php
@@ -42,6 +42,14 @@ function get_course_data($from, $number_of_items, $column, $direction, $dataFunc
     $addTeacherColumn = true;
     $table = Database::get_main_table(TABLE_MAIN_COURSE);
 
+    $from = (int) $from;
+    $number_of_items = (int) $number_of_items;
+    $column = (int) $column;
+
+    if (!in_array(strtolower($direction), ['asc', 'desc'])) {
+        $direction = 'desc';
+    }
+
     $teachers = '';
     if ($addTeacherColumn) {
         $teachers = " GROUP_CONCAT(cu.user_id SEPARATOR ',') as col4, ";
diff --git a/main/admin/course_request_review.php b/main/admin/course_request_review.php
index 6be31c1616..eb58cb3c71 100755
--- a/main/admin/course_request_review.php
+++ b/main/admin/course_request_review.php
@@ -129,6 +129,11 @@ function get_request_data($from, $number_of_items, $column, $direction)
     global $keyword;
     $course_request_table = Database::get_main_table(TABLE_MAIN_COURSE_REQUEST);
 
+    $from = (int) $from;
+    $number_of_items = (int) $number_of_items;
+    $column = (int) $column;
+    $direction = !in_array(strtolower(trim($direction)), ['asc', 'desc']) ? 'asc' : $direction;
+
     if (DELETE_ACTION_ENABLED) {
         $sql = "SELECT id AS col0,
                    code AS col1,
@@ -177,7 +182,7 @@ function get_request_data($from, $number_of_items, $column, $direction)
 function email_filter($teacher)
 {
     $teacher = Database::escape_string($teacher);
-    $sql = "SELECT user_id FROM ".Database::get_main_table(TABLE_MAIN_COURSE_REQUEST)." 
+    $sql = "SELECT user_id FROM ".Database::get_main_table(TABLE_MAIN_COURSE_REQUEST)."
             WHERE tutor_name LIKE '".$teacher."'";
     $res = Database::query($sql);
     $info = Database::fetch_array($res);
diff --git a/main/admin/settings.lib.php b/main/admin/settings.lib.php
index 3e5ac2b857..18d6bdf399 100755
--- a/main/admin/settings.lib.php
+++ b/main/admin/settings.lib.php
@@ -1279,6 +1279,11 @@ function getTemplateData($from, $number_of_items, $column, $direction)
     // Database table definition.
     $table_system_template = Database::get_main_table('system_template');
 
+    $from = (int) $from;
+    $number_of_items = (int) $number_of_items;
+    $column = (int) $column;
+    $direction = !in_array(strtolower(trim($direction)), ['asc', 'desc']) ? 'asc' : $direction;
+
     // The sql statement.
     $sql = "SELECT image as col0, title as col1, id as col2 FROM $table_system_template";
     $sql .= " ORDER BY col$column $direction ";
diff --git a/main/cron/lang/langstats.class.php b/main/cron/lang/langstats.class.php
index 60c630d125..02a15830aa 100755
--- a/main/cron/lang/langstats.class.php
+++ b/main/cron/lang/langstats.class.php
@@ -152,8 +152,10 @@ class langstats
      */
     public function get_popular_terms($num = 1000)
     {
+        $num = (int) $num;
         $res = $this->db->query(
-            'SELECT * FROM lang_freq ORDER BY term_count DESC LIMIT '.$num
+            'SELECT * FROM lang_freq
+                  ORDER BY term_count DESC LIMIT '.$num
         );
         $list = [];
         while ($row = $res->fetchArray()) {
diff --git a/main/exercise/TestCategory.php b/main/exercise/TestCategory.php
index ce8c68bbb1..90be5b5c21 100644
--- a/main/exercise/TestCategory.php
+++ b/main/exercise/TestCategory.php
@@ -236,7 +236,7 @@ class TestCategory
             $field = Database::escape_string($field);
             $sql = "SELECT $field FROM $table
                     WHERE c_id = $courseId
-                    ORDER BY $field ASC";
+                    ORDER BY `$field` ASC";
             $res = Database::query($sql);
             while ($row = Database::fetch_array($res)) {
                 $categories[] = $row[$field];
diff --git a/main/exercise/exercise.class.php b/main/exercise/exercise.class.php
index 1a1550d30f..6ac6396ae3 100755
--- a/main/exercise/exercise.class.php
+++ b/main/exercise/exercise.class.php
@@ -666,7 +666,7 @@ class Exercise
             if (!empty($sidx) && !empty($sord)) {
                 if ('question' === $sidx) {
                     if (in_array(strtolower($sord), ['desc', 'asc'])) {
-                        $orderCondition = " ORDER BY q.$sidx $sord";
+                        $orderCondition = " ORDER BY `q.$sidx` $sord";
                     }
                 }
             }
diff --git a/main/forum/forumfunction.inc.php b/main/forum/forumfunction.inc.php
index 13773f6b6f..d9c37572e4 100755
--- a/main/forum/forumfunction.inc.php
+++ b/main/forum/forumfunction.inc.php
@@ -6128,6 +6128,7 @@ function get_thread_user_post_limit($course_code, $thread_id, $user_id, $limit =
 
     $course_info = api_get_course_info($course_code);
     $course_id = $course_info['real_id'];
+    $limit = (int) $limit;
 
     $sql = "SELECT * FROM $table_posts posts
             LEFT JOIN  $table_users users
@@ -6136,7 +6137,8 @@ function get_thread_user_post_limit($course_code, $thread_id, $user_id, $limit =
                 posts.c_id = $course_id AND
                 posts.thread_id='".Database::escape_string($thread_id)."' AND
                 posts.poster_id='".Database::escape_string($user_id)."'
-            ORDER BY posts.post_id DESC LIMIT $limit ";
+            ORDER BY posts.post_id DESC
+            LIMIT $limit ";
     $result = Database::query($sql);
     $post_list = [];
     while ($row = Database::fetch_array($result)) {
diff --git a/main/group/group_space.php b/main/group/group_space.php
index f663a5f944..d9ddec97bb 100755
--- a/main/group/group_space.php
+++ b/main/group/group_space.php
@@ -424,6 +424,7 @@ function get_number_of_group_users()
  */
 function get_group_user_data($from, $number_of_items, $column, $direction)
 {
+    $direction = !in_array(strtolower(trim($direction)), ['asc', 'desc']) ? 'asc' : $direction;
     $groupInfo = GroupManager::get_group_properties(api_get_group_id());
     $course_id = api_get_course_int_id();
     $column = (int) $column;
diff --git a/main/inc/ajax/exercise.ajax.php b/main/inc/ajax/exercise.ajax.php
index b2038dc249..8aaf248a6f 100755
--- a/main/inc/ajax/exercise.ajax.php
+++ b/main/inc/ajax/exercise.ajax.php
@@ -241,7 +241,7 @@ switch ($action) {
                     GROUP BY exe_user_id
                 ) as aa
                 ON aa.exe_user_id = user_id
-                ORDER BY $sidx $sord
+                ORDER BY `$sidx` $sord
                 LIMIT $start, $limit";
 
         $result = Database::query($sql);
diff --git a/main/inc/ajax/model.ajax.php b/main/inc/ajax/model.ajax.php
index 3f52204ba3..8d4956d9d1 100755
--- a/main/inc/ajax/model.ajax.php
+++ b/main/inc/ajax/model.ajax.php
@@ -1015,7 +1015,7 @@ switch ($action) {
 
         $result = $manager->get_all([
             'where' => ['c_id = ? ' => $courseId],
-            'order' => "$sidx $sord",
+            'order' => "`$sidx` $sord",
             'LIMIT' => "$start , $limit",
         ]);
         break;
@@ -1068,7 +1068,7 @@ switch ($action) {
             $object->table,
             [
                 'where' => ['session_id = ? ' => $sessionId],
-                'order' => "$sidx $sord",
+                'order' => "`$sidx` $sord",
                 'LIMIT' => "$start , $limit", ]
         );
         if ($result) {
@@ -1231,7 +1231,7 @@ switch ($action) {
                 null,
                 null,
                 "LIMIT $start, $limit",
-                " $sidx $sord",
+                " `$sidx` $sord",
                 null,
                 null,
                 true,
@@ -1251,7 +1251,7 @@ switch ($action) {
             null,
             null,
             "LIMIT $start, $limit",
-            " $sidx $sord",
+            " `$sidx` $sord",
             null,
             null,
             true,
@@ -1909,7 +1909,7 @@ switch ($action) {
                 $result = SessionManager::get_sessions_admin_complete(
                     [
                         'where' => $whereCondition,
-                        'order' => "$sidx $sord, s.name",
+                        'order' => "`$sidx` $sord, s.name",
                         'extra' => $extra_fields,
                         'limit' => "$start , $limit",
                     ]
@@ -1922,7 +1922,7 @@ switch ($action) {
                 $result = SessionManager::formatSessionsAdminForGrid(
                     [
                         'where' => $whereCondition,
-                        'order' => "$sidx $sord, s.name",
+                        'order' => "`$sidx` $sord, s.name",
                         'extra' => $extra_fields,
                         'limit' => "$start , $limit",
                     ],
@@ -1964,7 +1964,7 @@ switch ($action) {
             $date_to,
             [
                 'where' => $whereCondition,
-                'order' => "$sidx $sord",
+                'order' => "`$sidx` $sord",
                 'limit' => "$start , $limit",
             ]
         );
@@ -2000,7 +2000,7 @@ switch ($action) {
             $date_to,
             [
                 'where' => $whereCondition,
-                'order' => "$sidx $sord",
+                'order' => "`$sidx` $sord",
                 'limit' => "$start , $limit",
             ]
         );
@@ -2041,7 +2041,7 @@ switch ($action) {
             $date_to,
             [
                 'where' => $whereCondition,
-                'order' => "$sidx $sord",
+                'order' => "`$sidx` $sord",
                 'limit' => "$start , $limit",
             ]
         );
@@ -2104,7 +2104,7 @@ switch ($action) {
             null,
             [
                 'where' => $whereCondition,
-                'order' => "$sidx $sord",
+                'order' => "`$sidx` $sord",
                 'limit' => "$start , $limit",
             ]
         );
@@ -2139,7 +2139,7 @@ switch ($action) {
             $date_from,
             [
                 'where' => $whereCondition,
-                'order' => "$sidx $sord",
+                'order' => "`$sidx` $sord",
                 'limit' => "$start , $limit",
             ]
         );
@@ -2158,7 +2158,7 @@ switch ($action) {
                 'where' => [
                     'parent_id = ? AND c_id = ?' => ['0', $course_id],
                 ],
-                'order' => "$sidx $sord",
+                'order' => "`$sidx` $sord",
                 'LIMIT' => "$start , $limit",
             ]
         );
@@ -2184,7 +2184,7 @@ switch ($action) {
         $result = Database::select(
             '*',
             $obj->table,
-            ['order' => "$sidx $sord", 'LIMIT' => "$start , $limit"]
+            ['order' => "`$sidx` $sord", 'LIMIT' => "$start , $limit"]
         );
         $new_result = [];
         foreach ($result as $item) {
@@ -2239,7 +2239,7 @@ switch ($action) {
         $result = Database::select(
             '*',
             $obj->table,
-            ['order' => "$sidx $sord", 'LIMIT' => "$start , $limit"]
+            ['order' => "`$sidx` $sord", 'LIMIT' => "$start , $limit"]
         );
         $new_result = [];
         foreach ($result as $item) {
@@ -2265,7 +2265,7 @@ switch ($action) {
         $result = Database::select(
             '*',
             $obj->table,
-            ['order' => "$sidx $sord", 'LIMIT' => "$start , $limit"]
+            ['order' => "`$sidx` $sord", 'LIMIT' => "$start , $limit"]
         );
         $new_result = [];
         foreach ($result as $item) {
@@ -2285,7 +2285,7 @@ switch ($action) {
         $result = Database::select(
             'p.id,p.name, p.description, c.name as career, p.status',
             "$obj->table p LEFT JOIN ".Database::get_main_table(TABLE_CAREER)." c  ON c.id = p.career_id ",
-            ['order' => "$sidx $sord", 'LIMIT' => "$start , $limit"]
+            ['order' => "`$sidx` $sord", 'LIMIT' => "$start , $limit"]
         );
 
         $new_result = [];
@@ -2312,7 +2312,7 @@ switch ($action) {
             $obj->table,
             [
                 'where' => ['url_id = ? ' => api_get_current_access_url_id()],
-                'order' => "$sidx $sord",
+                'order' => "`$sidx` $sord",
                 'LIMIT' => "$start , $limit",
             ]
         );
@@ -2331,7 +2331,7 @@ switch ($action) {
         $result = Database::select(
             '*',
             "$obj->table ",
-            ['order' => "$sidx $sord", 'LIMIT' => "$start , $limit"]
+            ['order' => "`$sidx` $sord", 'LIMIT' => "$start , $limit"]
         );
         $new_result = [];
         foreach ($result as $item) {
@@ -2491,7 +2491,7 @@ switch ($action) {
         $columns = ['display_text', 'option_value', 'option_order'];
         $result = $obj->get_all([
             'where' => ['field_id = ? ' => $field_id],
-            'order' => "$sidx $sord",
+            'order' => "`$sidx` $sord",
             'LIMIT' => "$start , $limit",
         ]);
         break;
@@ -2516,10 +2516,7 @@ switch ($action) {
                 );
                 break;
             case 'registered':
-                $result = $obj->getUserGroupInCourse(
-                    $options,
-                    $groupFilter
-                );
+                $result = $obj->getUserGroupInCourse($options, $groupFilter);
                 break;
         }
 
diff --git a/main/inc/lib/TicketManager.php b/main/inc/lib/TicketManager.php
index 0ee2e6587f..aec9e4ad67 100644
--- a/main/inc/lib/TicketManager.php
+++ b/main/inc/lib/TicketManager.php
@@ -930,7 +930,7 @@ class TicketManager
                      )
             )";
         }
-        $sql .= " ORDER BY $column $direction";
+        $sql .= " ORDER BY `$column` $direction";
         $sql .= " LIMIT $from, $number_of_items";
 
         $result = Database::query($sql);
diff --git a/main/inc/lib/agenda.lib.php b/main/inc/lib/agenda.lib.php
index 73e00517ad..900bffa356 100644
--- a/main/inc/lib/agenda.lib.php
+++ b/main/inc/lib/agenda.lib.php
@@ -1240,9 +1240,7 @@ class Agenda
                         if (!empty($sessionList)) {
                             foreach ($sessionList as $sessionItem) {
                                 $sessionId = $sessionItem['id'];
-                                $courses = SessionManager::get_course_list_by_session_id(
-                                    $sessionId
-                                );
+                                $courses = SessionManager::get_course_list_by_session_id($sessionId);
                                 $sessionInfo = [
                                     'session_id' => $sessionId,
                                     'courses' => $courses,
@@ -3404,9 +3402,14 @@ class Agenda
 
         $current_access_url_id = api_get_current_access_url_id();
 
-        if ($type == "month_view" or $type == "") {
+        if ($type == "month_view" || $type == "") {
             // We are in month view
-            $sql = "SELECT * FROM ".$tbl_global_agenda." WHERE MONTH(start_date) = ".$month." AND YEAR(start_date) = ".$year."  AND access_url_id = $current_access_url_id ORDER BY start_date ASC";
+            $sql = "SELECT * FROM ".$tbl_global_agenda."
+                    WHERE
+                        MONTH(start_date) = ".$month." AND
+                        YEAR(start_date) = ".$year."  AND
+                        access_url_id = $current_access_url_id
+                    ORDER BY start_date ASC";
         }
         // 2. creating the SQL statement for getting the personal agenda items in WEEK view
         if ($type == "week_view") { // we are in week view
@@ -3537,9 +3540,14 @@ class Agenda
         $user_id = intval($user_id);
 
         // 1. creating the SQL statement for getting the personal agenda items in MONTH view
-        if ($type == "month_view" or $type == "") {
+        if ($type === "month_view" || $type === "") {
             // we are in month view
-            $sql = "SELECT * FROM ".$tbl_personal_agenda." WHERE user='".$user_id."' and MONTH(date)='".$month."' AND YEAR(date) = '".$year."'  ORDER BY date ASC";
+            $sql = "SELECT * FROM $tbl_personal_agenda
+                    WHERE
+                        user='".$user_id."' AND
+                        MONTH(date)='".$month."' AND
+                        YEAR(date) = '".$year."'
+                     ORDER BY date ASC";
         }
 
         // 2. creating the SQL statement for getting the personal agenda items in WEEK view
diff --git a/main/inc/lib/api.lib.php b/main/inc/lib/api.lib.php
index 9b9eb8f2eb..cf28131ea5 100644
--- a/main/inc/lib/api.lib.php
+++ b/main/inc/lib/api.lib.php
@@ -5070,7 +5070,8 @@ function api_get_languages()
 function api_get_languages_to_array()
 {
     $tbl_language = Database::get_main_table(TABLE_MAIN_LANGUAGE);
-    $sql = "SELECT * FROM $tbl_language WHERE available='1' ORDER BY original_name ASC";
+    $sql = "SELECT * FROM $tbl_language
+            WHERE available='1' ORDER BY original_name ASC";
     $result = Database::query($sql);
     $languages = [];
     while ($row = Database::fetch_array($result)) {
@@ -6223,11 +6224,13 @@ function api_get_access_urls($from = 0, $to = 1000000, $order = 'url', $directio
     $table = Database::get_main_table(TABLE_MAIN_ACCESS_URL);
     $from = (int) $from;
     $to = (int) $to;
-    $order = Database::escape_string($order, null, false);
-    $direction = Database::escape_string($direction, null, false);
+    $order = Database::escape_string($order);
+    $direction = Database::escape_string($direction);
+    $direction = !in_array(strtolower(trim($direction)), ['asc', 'desc']) ? 'asc' : $direction;
+
     $sql = "SELECT id, url, description, active, created_by, tms
             FROM $table
-            ORDER BY $order $direction
+            ORDER BY `$order` $direction
             LIMIT $to OFFSET $from";
     $res = Database::query($sql);
 
diff --git a/main/inc/lib/course.lib.php b/main/inc/lib/course.lib.php
index f56329f3d3..bfddfe8135 100755
--- a/main/inc/lib/course.lib.php
+++ b/main/inc/lib/course.lib.php
@@ -239,7 +239,7 @@ class CourseManager
         }
 
         if (!empty($orderby)) {
-            $sql .= " ORDER BY ".Database::escape_string($orderby)." ";
+            $sql .= " ORDER BY `".Database::escape_string($orderby)."` ";
         } else {
             $sql .= ' ORDER BY 1 ';
         }
@@ -247,11 +247,11 @@ class CourseManager
         if (!in_array($orderdirection, ['ASC', 'DESC'])) {
             $sql .= 'ASC';
         } else {
-            $sql .= ($orderdirection == 'ASC' ? 'ASC' : 'DESC');
+            $sql .= ($orderdirection === 'ASC' ? 'ASC' : 'DESC');
         }
 
         if (!empty($howmany) && is_int($howmany) and $howmany > 0) {
-            $sql .= ' LIMIT '.Database::escape_string($howmany);
+            $sql .= ' LIMIT '.(int) $howmany;
         } else {
             $sql .= ' LIMIT 1000000'; //virtually no limit
         }
@@ -1534,7 +1534,7 @@ class CourseManager
         // we have to check if it is a valid field that can be sorted on
         if (!strstr($order_by, 'ORDER BY')) {
             if (!empty($order_by)) {
-                $order_by = "ORDER BY $order_by";
+                $order_by = "ORDER BY $order_by ";
             } else {
                 $order_by = '';
             }
diff --git a/main/inc/lib/database.lib.php b/main/inc/lib/database.lib.php
index 18ffddc694..ea9752776c 100755
--- a/main/inc/lib/database.lib.php
+++ b/main/inc/lib/database.lib.php
@@ -665,7 +665,7 @@ class Database
                             }
                         } else {
                             $value_array = self::escape_string($value_array);
-                            $clean_values = $value_array;
+                            $clean_values = [$value_array];
                         }
 
                         if (!empty($condition) && $clean_values != '') {
@@ -693,7 +693,7 @@ class Database
 
                     if (!empty($order_array)) {
                         // 'order' => 'id desc, name desc'
-                        $order_array = self::escape_string($order_array, null, false);
+                        $order_array = self::escape_string($order_array);
                         $new_order_array = explode(',', $order_array);
                         $temp_value = [];
 
@@ -708,10 +708,10 @@ class Database
                                 if (in_array($element[1], ['desc', 'asc'])) {
                                     $order = $element[1];
                                 }
-                                $temp_value[] = $element[0].' '.$order.' ';
+                                $temp_value[] = ' `'.$element[0].'` '.$order.' ';
                             } else {
                                 //by default DESC
-                                $temp_value[] = $element[0].' DESC ';
+                                $temp_value[] = ' `'.$element[0].'` DESC ';
                             }
                         }
                         if (!empty($temp_value)) {
diff --git a/main/inc/lib/exercise.lib.php b/main/inc/lib/exercise.lib.php
index ef0cf4691a..ce5eb4738b 100644
--- a/main/inc/lib/exercise.lib.php
+++ b/main/inc/lib/exercise.lib.php
@@ -1987,8 +1987,9 @@ HOTSPOT;
         }
         $in_hotpot_path = Database::escape_string($in_hotpot_path);
         $in_direction = Database::escape_string($in_direction);
+        $in_direction = !in_array(strtolower(trim($in_direction)), ['asc', 'desc']) ? 'asc' : $in_direction;
         $in_column = Database::escape_string($in_column);
-        $in_number_of_items = intval($in_number_of_items);
+        $in_number_of_items = (int) $in_number_of_items;
         $in_from = (int) $in_from;
 
         $TBL_TRACK_HOTPOTATOES = Database::get_main_table(
@@ -2012,7 +2013,7 @@ HOTSPOT;
         }
         // get a number of sorted results
         $sql .= " $where_condition
-            ORDER BY $in_column $in_direction
+            ORDER BY `$in_column` $in_direction
             LIMIT $in_from, $in_number_of_items";
 
         $res = Database::query($sql);
@@ -2448,9 +2449,10 @@ HOTSPOT;
             $column = !empty($column) ? Database::escape_string($column) : null;
             $from = (int) $from;
             $number_of_items = (int) $number_of_items;
+            $direction = !in_array(strtolower(trim($direction)), ['asc', 'desc']) ? 'asc' : $direction;
 
             if (!empty($column)) {
-                $sql .= " ORDER BY $column $direction ";
+                $sql .= " ORDER BY `$column` $direction ";
             }
 
             if (!$getOnlyIds) {
diff --git a/main/inc/lib/groupmanager.lib.php b/main/inc/lib/groupmanager.lib.php
index caf6883cb9..741a3a5d22 100755
--- a/main/inc/lib/groupmanager.lib.php
+++ b/main/inc/lib/groupmanager.lib.php
@@ -1,4 +1,5 @@
 <?php
+
 /* For licensing terms, see /license.txt */
 
 use Chamilo\CourseBundle\Entity\CGroupRelUser;
@@ -1233,9 +1234,9 @@ class GroupManager
                     g.id = $group_id";
 
         if (!empty($column) && !empty($direction)) {
-            $column = Database::escape_string($column, null, false);
-            $direction = ('ASC' == $direction ? 'ASC' : 'DESC');
-            $sql .= " ORDER BY $column $direction";
+            $column = Database::escape_string($column);
+            $direction = ('ASC' === $direction ? 'ASC' : 'DESC');
+            $sql .= " ORDER BY `$column` $direction";
         }
 
         if (!empty($start) && !empty($limit)) {
diff --git a/main/inc/lib/myspace.lib.php b/main/inc/lib/myspace.lib.php
index 20abec7713..5aed51fa74 100644
--- a/main/inc/lib/myspace.lib.php
+++ b/main/inc/lib/myspace.lib.php
@@ -552,7 +552,7 @@ class MySpace
             }
         }
         if (!empty($order[$tracking_column])) {
-            $sqlCoachs .= ' ORDER BY '.$order[$tracking_column].' '.$tracking_direction;
+            $sqlCoachs .= " ORDER BY `".$order[$tracking_column]."` ".$tracking_direction;
         }
 
         $result_coaches = Database::query($sqlCoachs);
@@ -3041,9 +3041,10 @@ class MySpace
             $direction = 'ASC';
         }
 
-        $column = intval($column);
-        $from = intval($from);
-        $number_of_items = intval($number_of_items);
+        $column = (int) $column;
+        $from = (int) $from;
+        $number_of_items = (int) $number_of_items;
+
         $sql .= " ORDER BY col$column $direction ";
         $sql .= " LIMIT $from,$number_of_items";
 
@@ -3173,7 +3174,7 @@ class MySpace
         }
 
         $order = [
-            "$column $direction",
+            " `$column` $direction",
         ];
         $userList = UserManager::get_user_list([], $order, $from, $numberItems);
         $return = [];
@@ -3874,6 +3875,7 @@ class MySpace
         $numberItems = (int) $numberItems;
         $column = (int) $column;
         $orderDirection = Database::escape_string($orderDirection);
+        $orderDirection = !in_array(strtolower(trim($orderDirection)), ['asc', 'desc']) ? 'asc' : $orderDirection;
 
         $user = Database::get_main_table(TABLE_MAIN_USER);
         $course = Database::get_main_table(TABLE_MAIN_COURSE);
diff --git a/main/inc/lib/notebook.lib.php b/main/inc/lib/notebook.lib.php
index a77b52b60f..3b26a8b375 100755
--- a/main/inc/lib/notebook.lib.php
+++ b/main/inc/lib/notebook.lib.php
@@ -274,12 +274,12 @@ class NotebookManager
 
         // Database table definition
         $table = Database::get_course_table(TABLE_NOTEBOOK);
-        $order_by = ' ORDER BY '.$notebookView." $sort_direction ";
+        $order_by = " ORDER BY `$notebookView` $sort_direction ";
 
         // Condition for the session
         $condition_session = api_get_session_condition($sessionId);
 
-        $cond_extra = $notebookView == 'update_date' ? " AND update_date <> ''" : ' ';
+        $cond_extra = $notebookView === 'update_date' ? " AND update_date <> ''" : ' ';
         $course_id = api_get_course_int_id();
 
         $sql = "SELECT * FROM $table
diff --git a/main/inc/lib/online.inc.php b/main/inc/lib/online.inc.php
index 1581c5c9a2..daa27eca24 100755
--- a/main/inc/lib/online.inc.php
+++ b/main/inc/lib/online.inc.php
@@ -1,4 +1,5 @@
 <?php
+
 /* For licensing terms, see /license.txt */
 
 use ChamiloSession as Session;
@@ -10,11 +11,6 @@ use ChamiloSession as Session;
  * @author Denes Nagy, principal author
  * @author Bart Mollet
  * @author Roan Embrechts, cleaning and bugfixing
- *
- * @package chamilo.whoisonline
- */
-
-/**
  * Insert a login reference for the current user into the track_e_online stats
  * table. This table keeps trace of the last login. Nothing else matters (we
  * don't keep traces of anything older).
@@ -334,14 +330,14 @@ function who_is_online(
                     friend_user_id <> '".api_get_user_id()."' AND
                     relation_type='".USER_RELATION_TYPE_FRIEND."' AND
                     user_id = '".api_get_user_id()."'
-                  ORDER BY $column $direction
+                  ORDER BY `$column` $direction
                   LIMIT $from, $number_of_items";
     } else {
         $query = "SELECT DISTINCT login_user_id, login_date
                     FROM ".$track_online_table." e
                     INNER JOIN ".$table_user." u ON (u.id = e.login_user_id)
                   WHERE u.status != ".ANONYMOUS." AND login_date >= '".$current_date."'
-                  ORDER BY $column $direction
+                  ORDER BY `$column` $direction
                   LIMIT $from, $number_of_items";
     }
 
@@ -357,7 +353,7 @@ function who_is_online(
                                     login_date >= '".$current_date."' AND
                                     friend_user_id <> '".api_get_user_id()."' AND
                                     relation_type='".USER_RELATION_TYPE_FRIEND."'
-                            ORDER BY $column $direction
+                            ORDER BY `$column` $direction
                             LIMIT $from, $number_of_items";
             } else {
                 // all users online
@@ -367,7 +363,7 @@ function who_is_online(
                           ON (u.id=track.login_user_id)
                           WHERE u.status != ".ANONYMOUS." AND track.access_url_id =  $access_url_id AND
                                 login_date >= '".$current_date."'
-                          ORDER BY $column $direction
+                          ORDER BY `$column` $direction
                           LIMIT $from, $number_of_items";
             }
         }
diff --git a/main/inc/lib/sessionmanager.lib.php b/main/inc/lib/sessionmanager.lib.php
index d859fe24dc..53df9fb6d5 100755
--- a/main/inc/lib/sessionmanager.lib.php
+++ b/main/inc/lib/sessionmanager.lib.php
@@ -803,7 +803,7 @@ class SessionManager
         $options
     ) {
         //escaping vars
-        $sessionId = $sessionId == 'T' ? 'T' : intval($sessionId);
+        $sessionId = $sessionId === 'T' ? 'T' : intval($sessionId);
         $courseId = intval($courseId);
 
         //tables
@@ -813,7 +813,7 @@ class SessionManager
 
         $course = api_get_course_info_by_id($courseId);
         $sessionCond = 'and session_id = %s';
-        if ($sessionId == 'T') {
+        if ($sessionId === 'T') {
             $sessionCond = '';
         }
 
@@ -830,7 +830,7 @@ class SessionManager
 
         $order = null;
         if (!empty($options['order'])) {
-            $order = " ORDER BY ".$options['order'];
+            $order = " ORDER BY ".$options['order']." ";
         }
 
         $sql = "SELECT u.id as user_id, u.lastname, u.firstname, u.username, u.email, s.c_id
@@ -3347,7 +3347,7 @@ class SessionManager
             }
 
             if (!empty($order)) {
-                $sql_query .= " ORDER BY $order $direction ";
+                $sql_query .= " ORDER BY `$order` $direction ";
             }
         }
 
@@ -6286,7 +6286,7 @@ class SessionManager
 
         if (!empty($column) && !empty($direction)) {
             $column = str_replace('u.', '', $column);
-            $sql .= " ORDER BY $column $direction ";
+            $sql .= " ORDER BY `$column` $direction ";
         }
 
         $limitCondition = '';
diff --git a/main/inc/lib/statistics.lib.php b/main/inc/lib/statistics.lib.php
index 2c157eca18..c8e9be9a05 100644
--- a/main/inc/lib/statistics.lib.php
+++ b/main/inc/lib/statistics.lib.php
@@ -977,7 +977,7 @@ class Statistics
                    HAVING t.c_id <> ''
                    AND DATEDIFF( '".api_get_utc_datetime()."' , access_date ) <= ".$date_diff;
         }
-        $sql .= ' ORDER BY '.$columns[$column].' '.$sql_order[$direction];
+        $sql .= ' ORDER BY `'.$columns[$column].'` '.$sql_order[$direction];
         $from = ($page_nr - 1) * $per_page;
         $sql .= ' LIMIT '.$from.','.$per_page;
 
diff --git a/main/inc/lib/tracking.lib.php b/main/inc/lib/tracking.lib.php
index ab37e9fdc4..f258bdddf1 100755
--- a/main/inc/lib/tracking.lib.php
+++ b/main/inc/lib/tracking.lib.php
@@ -3784,7 +3784,7 @@ class Tracking
             if (in_array($orderByName, ['name', 'access_start_date'])) {
                 $orderByDirection = in_array(strtolower($orderByDirection), ['asc', 'desc']) ? $orderByDirection : 'asc';
                 $orderByName = Database::escape_string($orderByName);
-                $orderBy .= " ORDER BY $orderByName $orderByDirection";
+                $orderBy .= " ORDER BY `$orderByName` $orderByDirection";
             }
         }
 
@@ -7780,7 +7780,8 @@ class TrackingCourseLog
         $table_item_property = Database::get_course_table(TABLE_ITEM_PROPERTY);
         $table_user = Database::get_main_table(TABLE_MAIN_USER);
         $table_session = Database::get_main_table(TABLE_MAIN_SESSION);
-        $session_id = intval($session_id);
+        $column = (int) $column;
+        $direction = !in_array(strtolower(trim($direction)), ['asc', 'desc']) ? 'asc' : $direction;
 
         $sql = "SELECT
                     tool as col0,
diff --git a/main/inc/lib/usermanager.lib.php b/main/inc/lib/usermanager.lib.php
index 1e5ced3ef8..d72b2503a0 100755
--- a/main/inc/lib/usermanager.lib.php
+++ b/main/inc/lib/usermanager.lib.php
@@ -2874,7 +2874,7 @@ class UserManager
             $field_filter = (int) $field_filter;
             $sqlf .= " AND filter = $field_filter ";
         }
-        $sqlf .= " ORDER BY ".$columns[$column]." $sort_direction ";
+        $sqlf .= " ORDER BY `".$columns[$column]."` $sort_direction ";
         if ($number_of_items != 0) {
             $sqlf .= " LIMIT ".intval($from).','.intval($number_of_items);
         }
@@ -4468,7 +4468,9 @@ class UserManager
 
         // all the information of the field
         $sql = "SELECT DISTINCT id, tag from $table_user_tag
-                WHERE field_id = $field_id AND tag LIKE '$tag%' ORDER BY tag LIMIT $limit";
+                WHERE field_id = $field_id AND tag LIKE '$tag%'
+                ORDER BY tag
+                LIMIT $limit";
         $result = Database::query($sql);
         $return = [];
         if (Database::num_rows($result) > 0) {
@@ -5487,7 +5489,6 @@ class UserManager
                             $userConditions
                     )
                     $teacherSelect
-
                 ) as t1";
 
         if ($getSql) {
@@ -5511,7 +5512,7 @@ class UserManager
             if (!empty($column) && !empty($direction)) {
                 // Fixing order due the UNIONs
                 $column = str_replace('u.', '', $column);
-                $orderBy = " ORDER BY $column $direction ";
+                $orderBy = " ORDER BY `$column` $direction ";
             }
         }
 
diff --git a/main/inc/lib/zombie/zombie_manager.class.php b/main/inc/lib/zombie/zombie_manager.class.php
index b04b721bed..25185f9475 100755
--- a/main/inc/lib/zombie/zombie_manager.class.php
+++ b/main/inc/lib/zombie/zombie_manager.class.php
@@ -86,10 +86,10 @@ class ZombieManager
             $sql .= ' AND user.active = 1';
         }
 
-        $sql .= " ORDER BY $column $direction";
+        $sql .= " ORDER BY `$column` $direction";
         if (!is_null($from) && !is_null($count)) {
-            $count = intval($count);
-            $from = intval($from);
+            $count = (int) $count;
+            $from = (int) $from;
             $sql .= " LIMIT $from, $count ";
         }
 
diff --git a/main/session/session_category_list.php b/main/session/session_category_list.php
index a48011857c..77308b4cca 100644
--- a/main/session/session_category_list.php
+++ b/main/session/session_category_list.php
@@ -1,9 +1,8 @@
 <?php
+
 /* For licensing terms, see /license.txt */
 /**
  * List sessions categories.
- *
- * @package chamilo.admin
  */
 $cidReset = true;
 
@@ -87,7 +86,7 @@ if (isset($_GET['search']) && $_GET['search'] === 'advanced') {
                 ) as nbr_session
 	 			FROM $tbl_session_category sc
 	 			$where
-	 			ORDER BY $sort $order
+	 			ORDER BY `$sort` $order
 	 			LIMIT $from,".($limit + 1);
 
     $query_rows = "SELECT count(*) as total_rows
diff --git a/main/session/session_course_list.php b/main/session/session_course_list.php
index 7ff5a7801a..f7a7ca00cb 100644
--- a/main/session/session_course_list.php
+++ b/main/session/session_course_list.php
@@ -57,7 +57,7 @@ $from = $page * $limit;
 $sql = "SELECT c.id, c.code, c.title, nbr_users
 		FROM $tbl_session_rel_course, $tbl_course c
 		WHERE c_id = c.id AND session_id='$id_session'
-		ORDER BY $sort
+		ORDER BY `$sort`
 		LIMIT $from,".($limit + 1);
 $result = Database::query($sql);
 $Courses = Database::store_result($result);
diff --git a/main/session/session_course_user_list.php b/main/session/session_course_user_list.php
index 4240105e17..cf459f5fab 100644
--- a/main/session/session_course_user_list.php
+++ b/main/session/session_course_user_list.php
@@ -101,7 +101,7 @@ $sql = "
     WHERE
         s.session_id = $id_session AND
         url.access_url_id = $urlId
-    ORDER BY $sort $direction
+    ORDER BY `$sort` $direction
     LIMIT $from,".($limit + 1);
 
 if ($direction === 'desc') {
diff --git a/main/user/subscribe_user.php b/main/user/subscribe_user.php
index 8571ff982f..d5dbcf6bfd 100755
--- a/main/user/subscribe_user.php
+++ b/main/user/subscribe_user.php
@@ -659,6 +659,8 @@ function get_user_data($from, $number_of_items, $column, $direction)
     }
 
     $sql .= " AND u.status != ".ANONYMOUS." ";
+    $column = (int) $column;
+    $direction = !in_array(strtolower(trim($direction)), ['asc', 'desc']) ? 'asc' : $direction;
     // Sorting and pagination (used by the sortable table)
     $sql .= " ORDER BY col$column $direction ";
     $from = (int) $from;
diff --git a/main/webservices/cm_webservice_inbox.php b/main/webservices/cm_webservice_inbox.php
index f22364d940..dffd498046 100755
--- a/main/webservices/cm_webservice_inbox.php
+++ b/main/webservices/cm_webservice_inbox.php
@@ -20,8 +20,8 @@ class WSCMInbox extends WSCM
             $user_id = UserManager::get_user_id_from_username($username);
             $condition_msg_status = ' msg_status = 1 '; // define('MESSAGE_STATUS_UNREAD', '1');
 
-            $sql_query = "SELECT COUNT(*) as number_messages 
-                          FROM $table_message 
+            $sql_query = "SELECT COUNT(*) as number_messages
+                          FROM $table_message
                           WHERE $condition_msg_status AND user_receiver_id=".$user_id;
 
             $sql_result = Database::query($sql_query);
@@ -107,13 +107,17 @@ class WSCMInbox extends WSCM
         $from,
         $number_of_items
     ) {
+        $from = (int) $from;
+        $number_of_items = (int) $number_of_items;
+
         if ($this->verifyUserPass($username, $password) == "valid") {
             $user_id = UserManager::get_user_id_from_username($username);
 
             $table_message = Database::get_main_table(TABLE_MESSAGE);
-            $sql_query = "SELECT id FROM $table_message 
-                          WHERE user_sender_id=".$user_id." AND msg_status=".MESSAGE_STATUS_OUTBOX." 					 
-                          ORDER BY send_date LIMIT $from,$number_of_items";
+            $sql_query = "SELECT id FROM $table_message
+                          WHERE user_sender_id=".$user_id." AND msg_status=".MESSAGE_STATUS_OUTBOX."
+                          ORDER BY send_date
+                          LIMIT $from,$number_of_items";
 
             $sql_result = Database::query($sql_query);
             $message = "#";
@@ -122,9 +126,9 @@ class WSCMInbox extends WSCM
             }
 
             return $message;
-        } else {
-            return get_lang('InvalidId');
         }
+
+        return get_lang('InvalidId');
     }
 
     public function get_message_data_sent($username, $password, $id, $field)
@@ -204,7 +208,7 @@ class WSCMInbox extends WSCM
     protected function set_message_as_read($user_id, $message_id)
     {
         $table_message = Database::get_main_table(TABLE_MESSAGE);
-        $query = "UPDATE $table_message SET msg_status = '".MESSAGE_STATUS_NEW."' 
+        $query = "UPDATE $table_message SET msg_status = '".MESSAGE_STATUS_NEW."'
                   WHERE user_receiver_id=".$user_id." AND id='".$message_id."';";
         Database::query($query);
     }
diff --git a/main/webservices/cm_webservice_user.php b/main/webservices/cm_webservice_user.php
index 87187271f0..4b5fe04d69 100755
--- a/main/webservices/cm_webservice_user.php
+++ b/main/webservices/cm_webservice_user.php
@@ -196,7 +196,7 @@ class WSCMUser extends WSCM
         }
         $order = '';
         foreach ($order_by as $orderByItem) {
-            $order .= Database::escape_string($orderByItem, null, false).', ';
+            $order .= Database::escape_string($orderByItem).', ';
         }
         $order = substr($order, 0, -2);
         if (count($order_by) > 0) {
diff --git a/main/work/work.lib.php b/main/work/work.lib.php
index f3ec075c2e..93023364e6 100755
--- a/main/work/work.lib.php
+++ b/main/work/work.lib.php
@@ -1272,7 +1272,7 @@ function getWorkListStudent(
                 $where_condition
             ";
 
-    $sql .= " ORDER BY $column $direction ";
+    $sql .= " ORDER BY `$column` $direction ";
 
     if (!empty($start) && !empty($limit)) {
         $sql .= " LIMIT $start, $limit";
@@ -1469,7 +1469,7 @@ function getAllWorkListStudent(
                 $where
             ";
 
-    $sql .= " ORDER BY $column $direction ";
+    $sql .= " ORDER BY `$column` $direction ";
 
     if (!empty($start) && !empty($limit)) {
         $sql .= " LIMIT $start, $limit";
@@ -1628,7 +1628,7 @@ function getWorkListTeacher(
                     parent_id = 0 AND
                     post_group_id = $groupIid
                     $where_condition
-                ORDER BY $column $direction
+                ORDER BY `$column` $direction
                 LIMIT $start, $limit";
 
         $result = Database::query($sql);
@@ -1876,7 +1876,7 @@ function get_work_user_list_from_documents(
         return $result['count'];
     }
 
-    $sql .= " ORDER BY $column $direction";
+    $sql .= " ORDER BY `$column` $direction";
     $sql .= " LIMIT $start, $limit";
 
     $result = Database::query($sql);
@@ -2157,7 +2157,7 @@ function get_work_user_list(
                     $whereCondition
                     $condition_session
                     AND u.status != ".INVITEE."
-                ORDER BY $column $direction";
+                ORDER BY `$column` $direction";
 
         if (!empty($start) && !empty($limit)) {
             $sql .= " LIMIT $start, $limit";
@@ -2686,7 +2686,7 @@ function getAllWork(
                 $statusCondition
                 AND u.status != ".INVITEE;
 
-    $sql .= " ORDER BY $column $direction ";
+    $sql .= " ORDER BY `$column` $direction ";
 
     if (!empty($start) && !empty($limit)) {
         $sql .= " LIMIT $start, $limit";
@@ -5765,10 +5765,9 @@ function getWorkUserList($courseCode, $sessionId, $groupId, $start, $limit, $sid
         }
 
         $orderBy = null;
-
         if (!empty($sidx) && !empty($sord)) {
             if (in_array($sidx, ['firstname', 'lastname'])) {
-                $orderBy = "ORDER BY $sidx $sord";
+                $orderBy = "ORDER BY `$sidx` $sord";
             }
         }
 
diff --git a/plugin/notebookteacher/src/NotebookTeacher.php b/plugin/notebookteacher/src/NotebookTeacher.php
index 69659f4a5f..664c927657 100644
--- a/plugin/notebookteacher/src/NotebookTeacher.php
+++ b/plugin/notebookteacher/src/NotebookTeacher.php
@@ -301,9 +301,9 @@ class NotebookTeacher
         // Database table definition
         $tableNotebook = Database::get_main_table(NotebookTeacherPlugin::TABLE_NOTEBOOKTEACHER);
         if ($view == 'creation_date' || $view == 'update_date') {
-            $orderBy = " ORDER BY $view $sortDirection ";
+            $orderBy = " ORDER BY `$view` $sortDirection ";
         } else {
-            $orderBy = " ORDER BY $view $sortDirection ";
+            $orderBy = " ORDER BY `$view` $sortDirection ";
         }
 
         // condition for the session