通过php和html显示测验

I trying to display a quiz from a list of quizzes depending on the current topic the user has clicked (topics are called sessions). Sessions have exercises and on every exercise I want the option to go to the specific session quiz (A session has 5 exercises and 1 quiz). When the quiz button is clicked, I'm trying to display the quiz title and author using the current $session_id and linking that to the session_id from the quiz_list table in the database.

Nothing is displaying and I'm getting errors like:

Notice: Undefined index: session_id in C:\xampp\htdocs\project\quiz.php on line 8

Warning: mysqli_fetch_assoc() expects parameter 1 to be mysqli_result, boolean given in C:\xampp\htdocs\Project\quiz.php on line 13

exercise.php:

<?php 
    //build up array as iterate through while loop
   $sessions_quiz_array = array();
   $get_quiz = mysqli_query($con, "SELECT * FROM `quiz_list` WHERE `session_id` = $session_id");

   //fetches result row as an associative array
   while ($row_quizes = mysqli_fetch_assoc($get_quiz)) {
   $sessions_quiz_array[] = $row_quizes;

   }

   //sessions_quiz_array is the associative array being looped 
   foreach ($sessions_quiz_array as $key => $value) {
      $quiz_id = $value['id'];
      $quiz_title = $value['quiz_title'];
      $quiz_author = $value['quiz_author'];
      ?>

    <a id='button' href="quiz.php?id=<?php echo $quiz_id; ?>"> Quiz</a>


            <?php  } ?> 

quiz.php

   <?php 
   session_start(); 
   include("includes/database.php");
   ?>
    <?php 
        //gets current
        $session_id = $_GET['session_id'];

    $get_quiz = "SELECT * FROM `quiz_list` WHERE `session_id` = $session_id";

        $run_quiz = mysqli_query($con, $get_quiz);
        $quiz_info = mysqli_fetch_assoc($run_quiz);

     ?>
      <hr>
      <div>

        <h1><?php echo $quiz_info["id"]; ?> </h1>
        <br>
        <p><?php echo $quiz_info["quiz_title"]; ?></p>
        <br>
        <p><strong><?php echo $quiz_info["quiz_author"]; ?></strong></p>


      </div>
      <hr>

      <a href="interactive_training.php" class="button previous">&laquo; Back to Training</a>

Any help would be greatly appreciated.

In you file exercise.php your GET request is ID not session_id near quiz.php?id=

You need to make following change in your quiz.php file.

Change from

$session_id = $_GET['session_id'];

To

$session_id = $_GET['id'];

Addiotionally you can add check before executing whole page like

if(!isset($session_id))
{
    exit('Session ID is missing');
}

Your quiz.php becomes:-

replace this

 $session_id = $_GET['session_id'];

with

 $session_id = $_GET['id'];