diff --git a/main/exercise/answer.class.php b/main/exercise/answer.class.php
index 3a1c0c5737..6102ca5a9f 100755
--- a/main/exercise/answer.class.php
+++ b/main/exercise/answer.class.php
@@ -125,7 +125,7 @@ class Answer
 
         $sql = "SELECT * FROM $table
                 WHERE
-                    question_id ='".$questionId."'
+                    question_id = $questionId
                 ORDER BY position";
 
         $result = Database::query($sql);
@@ -210,7 +210,7 @@ class Answer
 
         $sql = "SELECT id FROM
               $table
-              WHERE question_id ='".$questionId."'";
+              WHERE question_id = $questionId";
 
         $result = Database::query($sql);
         $id = [];
@@ -394,7 +394,7 @@ class Answer
         $table = Database::get_course_table(TABLE_QUIZ_ANSWER);
         $auto_id = (int) $auto_id;
         $sql = "SELECT iid, answer, id_auto FROM $table
-                WHERE id_auto='$auto_id'";
+                WHERE id_auto = $auto_id";
         $rs = Database::query($sql);
 
         if (Database::num_rows($rs) > 0) {
@@ -501,7 +501,7 @@ class Answer
     {
         $table = Database::get_course_table(TABLE_QUIZ_QUESTION);
         $sql = "SELECT type FROM $table
-                WHERE iid = '".$this->questionId."'";
+                WHERE iid = {$this->questionId}";
         $res = Database::query($sql);
         if (Database::num_rows($res) <= 0) {
             return null;
diff --git a/main/exercise/exercise.class.php b/main/exercise/exercise.class.php
index cda47281b2..e7084d68bf 100755
--- a/main/exercise/exercise.class.php
+++ b/main/exercise/exercise.class.php
@@ -179,7 +179,7 @@ class Exercise
         }
 
         $sql = "SELECT * FROM $table
-                WHERE iid = ".$id;
+                WHERE iid = $id";
         $result = Database::query($sql);
 
         // if the exercise has been found
@@ -665,14 +665,14 @@ class Exercise
                     FROM $TBL_EXERCICE_QUESTION e
                     INNER JOIN $TBL_QUESTIONS  q
                     ON e.question_id = q.iid
-					WHERE e.exercice_id	= '".$this->id."' AND e.c_id = {$this->course_id}";
+					WHERE e.exercice_id	= {$this->id} AND e.c_id = {$this->course_id}";
 
             $orderCondition = ' ORDER BY question_order ';
 
             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 $sord";
                     }
                 }
             }
diff --git a/main/exercise/question.class.php b/main/exercise/question.class.php
index 0669703cd8..ab7d08c981 100755
--- a/main/exercise/question.class.php
+++ b/main/exercise/question.class.php
@@ -869,7 +869,7 @@ abstract class Question
      *
      * @return bool - true if copied, otherwise false
      */
-    public function exportPicture($questionId, $courseInfo)
+    public function exportPicture(int $questionId, array $courseInfo)
     {
         if (empty($questionId) || empty($courseInfo)) {
             return false;
@@ -919,7 +919,7 @@ abstract class Question
         $table = Database::get_course_table(TABLE_QUIZ_QUESTION);
         $sql = "UPDATE $table SET
                 picture = '".Database::escape_string($picture)."'
-                WHERE iid='".intval($questionId)."'";
+                WHERE iid = $questionId";
         Database::query($sql);
 
         $documentId = add_document(
diff --git a/main/exercise/question_create.php b/main/exercise/question_create.php
index 4200b52686..15667036c6 100755
--- a/main/exercise/question_create.php
+++ b/main/exercise/question_create.php
@@ -82,8 +82,8 @@ if ($form->validate()) {
     $answer_type = $values['question_type_hidden'];
 
     // check feedback_type from current exercise for type of question delineation
-    $exercise_id = intval($values['exercise']);
-    $sql = "SELECT feedback_type FROM $tbl_exercises WHERE iid = '$exercise_id'";
+    $exercise_id = (int) $values['exercise'];
+    $sql = "SELECT feedback_type FROM $tbl_exercises WHERE iid = $exercise_id";
     $rs_feedback_type = Database::query($sql);
     $row_feedback_type = Database::fetch_row($rs_feedback_type);
     $feedback_type = $row_feedback_type[0];
diff --git a/main/exercise/unique_answer.class.php b/main/exercise/unique_answer.class.php
index 39ee4052b7..5e4aea2229 100755
--- a/main/exercise/unique_answer.class.php
+++ b/main/exercise/unique_answer.class.php
@@ -485,7 +485,7 @@ class UniqueAnswer extends Question
         $tbl_quiz_answer = Database::get_course_table(TABLE_QUIZ_ANSWER);
         $tbl_quiz_question = Database::get_course_table(TABLE_QUIZ_QUESTION);
         $course_id = api_get_course_int_id();
-        $question_id = intval($question_id);
+        $question_id = (int) $question_id;
         $score = floatval($score);
         $correct = intval($correct);
         $title = Database::escape_string($title);
@@ -528,7 +528,7 @@ class UniqueAnswer extends Question
         if ($correct) {
             $sql = "UPDATE $tbl_quiz_question
                     SET ponderation = (ponderation + $score)
-                    WHERE iid = ".$question_id;
+                    WHERE iid = $question_id";
             Database::query($sql);
         }
     }
diff --git a/main/extra/myStudents.php b/main/extra/myStudents.php
index a7b4c2f397..f2daa97d25 100644
--- a/main/extra/myStudents.php
+++ b/main/extra/myStudents.php
@@ -1119,7 +1119,7 @@ if (!empty($studentId)) {
 
             $sql = "SELECT quiz.title, iid FROM $t_quiz AS quiz
                             WHERE
-                                quiz.c_id = ".$courseInfo['real_id']." AND
+                                quiz.c_id = {$courseInfo['real_id']} AND
                                 active IN (0, 1)
                                 $sessionCondition
                             ORDER BY quiz.title ASC ";
@@ -2231,7 +2231,7 @@ if (empty($_GET['details'])) {
         ];
 
     $t_quiz = Database:: get_course_table(TABLE_QUIZ_TEST);
-    $sql = "SELECT quiz.title, iid FROM ".$t_quiz." AS quiz
+    $sql = "SELECT quiz.title, iid FROM $t_quiz AS quiz
                 WHERE
                     quiz.c_id = $c_id AND
                     (quiz.session_id = $session_id OR quiz.session_id = 0) AND
diff --git a/main/gradebook/lib/be/exerciselink.class.php b/main/gradebook/lib/be/exerciselink.class.php
index 6ccb8ba70c..894f705bde 100755
--- a/main/gradebook/lib/be/exerciselink.class.php
+++ b/main/gradebook/lib/be/exerciselink.class.php
@@ -638,9 +638,9 @@ class ExerciseLink extends AbstractLink
                 $this->exercise_data = Database::fetch_array($result);
             } else {
                 // Try with iid
-                $sql = 'SELECT * FROM '.$table.'
-                        WHERE
-                            iid = '.$exerciseId;
+                $sql = "SELECT * FROM $table
+                    WHERE
+                        iid = $exerciseId";
                 $result = Database::query($sql);
                 $rows = Database::num_rows($result);
 
@@ -648,9 +648,9 @@ class ExerciseLink extends AbstractLink
                     $this->exercise_data = Database::fetch_array($result);
                 } else {
                     // Try wit id
-                    $sql = 'SELECT * FROM '.$table.'
-                            WHERE
-                                iid = '.$exerciseId;
+                    $sql = "SELECT * FROM $table
+                        WHERE
+                            iid = $exerciseId";
                     $result = Database::query($sql);
                     $this->exercise_data = Database::fetch_array($result);
                 }
diff --git a/main/inc/lib/tracking.lib.php b/main/inc/lib/tracking.lib.php
index 080989fe72..5a8e5cefc7 100755
--- a/main/inc/lib/tracking.lib.php
+++ b/main/inc/lib/tracking.lib.php
@@ -384,11 +384,11 @@ class Tracking
                     $result_disabled_ext_all = false;
                     if ('quiz' === $row['item_type']) {
                         // Check results_disabled in quiz table.
-                        $my_path = Database::escape_string($row['path']);
+                        $lpItemPath = (int) $row['path'];
                         $sql = "SELECT results_disabled
                                 FROM $TBL_QUIZ
                                 WHERE
-                                    iid ='".$my_path."'";
+                                    iid = $lpItemPath";
                         $res_result_disabled = Database::query($sql);
                         $row_result_disabled = Database::fetch_row($res_result_disabled);
 
@@ -686,14 +686,13 @@ class Tracking
                     $my_id = $row['myid'];
                     $my_lp_id = $row['mylpid'];
                     $my_lp_view_id = $row['mylpviewid'];
-                    $my_path = $row['path'];
+                    $lpItemPath = (int) $row['path'];
                     $result_disabled_ext_all = false;
                     if ($row['item_type'] === 'quiz') {
                         // Check results_disabled in quiz table.
-                        $my_path = Database::escape_string($my_path);
                         $sql = "SELECT results_disabled
                                 FROM $TBL_QUIZ
-                                WHERE iid = '$my_path' ";
+                                WHERE iid = $lpItemPath";
                         $res_result_disabled = Database::query($sql);
                         $row_result_disabled = Database::fetch_row($res_result_disabled);
 
@@ -2982,7 +2981,7 @@ class Tracking
                         $num = Database::num_rows($result_last_attempt);
                         if ($num > 0) {
                             $attemptResult = Database::fetch_array($result_last_attempt, 'ASSOC');
-                            $id_last_attempt = $attemptResult['exe_id'];
+                            $id_last_attempt = (int) $attemptResult['exe_id'];
                             // We overwrite the score with the best one not the one saved in the LP (latest)
                             if ($getOnlyBestAttempt && $get_only_latest_attempt_results == false) {
                                 if ($debug) {
@@ -3007,7 +3006,7 @@ class Tracking
                                         INNER JOIN $tbl_quiz_questions AS q
                                         ON q.iid = at.question_id
                                         WHERE
-                                            exe_id ='$id_last_attempt' AND
+                                            exe_id = $id_last_attempt AND
                                             at.c_id = $course_id
                                     )
                                     AS t";
diff --git a/main/lp/learnpath.class.php b/main/lp/learnpath.class.php
index 74c457081a..bdb9dcff97 100755
--- a/main/lp/learnpath.class.php
+++ b/main/lp/learnpath.class.php
@@ -7686,7 +7686,7 @@ class learnpath
         } elseif (is_numeric($extra_info)) {
             $sql = "SELECT title, description
                     FROM $tbl_quiz
-                    WHERE iid = ".$extra_info;
+                    WHERE iid = $extra_info";
 
             $result = Database::query($sql);
             $row = Database::fetch_array($result);
diff --git a/src/Chamilo/CourseBundle/Component/CourseCopy/CourseBuilder.php b/src/Chamilo/CourseBundle/Component/CourseCopy/CourseBuilder.php
index 9c9be40fcc..63c8eeae2b 100644
--- a/src/Chamilo/CourseBundle/Component/CourseCopy/CourseBuilder.php
+++ b/src/Chamilo/CourseBundle/Component/CourseCopy/CourseBuilder.php
@@ -797,8 +797,8 @@ class CourseBuilder
             $this->findAndSetDocumentsInText($obj->description);
 
             $quiz = new Quiz($obj);
-            $sql = 'SELECT * FROM '.$table_rel.'
-                    WHERE c_id = '.$courseId.' AND exercice_id = '.$obj->iid;
+            $sql = "SELECT * FROM $table_rel
+                WHERE c_id = $courseId AND exercice_id = {$obj->iid}";
             $db_result2 = Database::query($sql);
             while ($obj2 = Database::fetch_object($db_result2)) {
                 $quiz->add_question($obj2->question_id, $obj2->question_order);
@@ -860,8 +860,8 @@ class CourseBuilder
             );
             $question->addPicture($this);
 
-            $sql = 'SELECT * FROM '.$table_ans.'
-                    WHERE question_id = '.$obj->iid;
+            $sql = "SELECT * FROM $table_ans
+                WHERE question_id = {$obj->iid}";
             $db_result2 = Database::query($sql);
             while ($obj2 = Database::fetch_object($db_result2)) {
                 $question->add_answer(
@@ -880,8 +880,8 @@ class CourseBuilder
 
                 if ($obj->type == MULTIPLE_ANSWER_TRUE_FALSE) {
                     $table_options = Database::get_course_table(TABLE_QUIZ_QUESTION_OPTION);
-                    $sql = 'SELECT * FROM '.$table_options.'
-                            WHERE question_id = '.$obj->iid;
+                    $sql = "SELECT * FROM $table_options
+                        WHERE question_id = {$obj->iid}";
                     $db_result3 = Database::query($sql);
                     while ($obj3 = Database::fetch_object($db_result3)) {
                         $question_option = new QuizQuestionOption($obj3);
@@ -951,7 +951,7 @@ class CourseBuilder
                         );
                         $question->addPicture($this);
                         $sql = "SELECT * FROM $table_ans
-                                WHERE question_id = ".$obj->id;
+                                WHERE question_id = {$obj->id}";
                         $db_result2 = Database::query($sql);
                         if (Database::num_rows($db_result2)) {
                             while ($obj2 = Database::fetch_object($db_result2)) {