Why is my quiz displaying the wrong 'correct answer'

Question

I am new to PHP, so I apologise if my question is quite primitive. I have made a quiz in PHP, and I intend for the quiz to find the correct answer for the currently displayed question. When the user submits an answer, the program should check if the answer submitted by the user matches the correct answer. However, my quiz changes the 'correctAnswer' variable before a point is awarded for a correct answer. I'm not sure how to fix this.

<?php

include('connect_db.php');

$sqlstmt = 'SELECT * FROM quiz ORDER BY RAND() LIMIT 1';

$res = mysqli_query($dbc, $sqlstmt);

while ($row = mysqli_fetch_assoc($res)) { 
  $CorrectAnswer = $row['CorrectAnswer'];
  echo $CorrectAnswer;
?>


<html>
  <head>
    <style>
    h1 {
      text-align: center;
    }
    .answer {
      display: flex;
      margin-inline: auto;
      margin-bottom: 1rem;
    }
    .button {
      margin-top: 1rem;
    }
    fieldset {
      display: flex;
      flex-direction: column;
      justify-content: center;
      width: 50rem;
      margin-inline: auto;
    }
    </style>
  </head>
  <body>
    <h1>Quiz</h1>
    <form method="POST" action="<?php echo $_SERVER['PHP_SELF'] ?>" align="center" id='myForm'>
      <fieldset >
        <legend>Question:</legend><br>
        <p><?php echo $row['Question']; ?></p><br>
        <div class="answer">
          <input type="radio" id="answer1" name="answer" value="<?php echo $row['Answer1']; ?>"><br>
          <label for="answer1"><?php echo $row['Answer1']; ?></label>
        </div>
        <div class="answer">
          <input type="radio" id="answer2" name="answer" value="<?php echo $row['Answer2']; ?>"><br>
          <label for="answer2"><?php echo $row['Answer2']; ?></label>
        </div>
        <div class="answer">
          <input type="radio" id="answer3" name="answer" value="<?php echo $row['Answer3']; ?>"><br>
          <label for="answer3"><?php echo $row['Answer3']; ?></label>
        </div>
        <div class="answer">          
          <input type="radio" id="answer4" name="answer" value="<?php echo $row['Answer4']; ?>"><br>
          <label for="answer4"><?php echo $row['Answer4']; ?></label>
        </div>
      </fieldset>
      <input class="button" type="submit" value="Submit">
    </form>
    <script>
      function validateForm() {
        var radios = document.getElementsByName('answer');
        var formValid = false;

        var i = 0;
        while (!formValid && i < radios.length) {
          if (radios[i].checked) formValid = true;
          i++;        
        }

        if (!formValid) alert("You must select an option!");
        return formValid;
      }

      var form = document.getElementById("myForm");
      form.onsubmit = validateForm;
</script>
    <?php



if (isset($_POST['answer'])) {
  $selectedAnswer = $_POST['answer'];
  echo $CorrectAnswer,$selectedAnswer;
  if ($selectedAnswer == $CorrectAnswer)
    echo '+1 pt';
  
}
}
?>
  </body>
</html>

I have tried changing the order that my variables are declared, thinking that this would match up the correct answer with the submitted answer, but I'm in my second week of learning PHP properly so I didn't really know what I was doing or what I was expecting.

Hi SpudOnPiano, welcome to SO! As Colleiflower already points out in [their answer](https://stackoverflow.com/a/74999960/1973005), a little more information on your database and what the exact output should be is required to fully answer your question. Please edit it so that others can help you better. — Axel Köhler, Jan 04 '23 at 13:41

score 1 · Answer 1 · answered Jan 04 '23 at 00:43

It's not clear what you mean by a point being awarded (there is only an echo function). It would be good if you could provide us with information from your SQL database, as your code correctly checks if $selectedAnswer is equal to $correctAnswer. The best way to solve this, based on the limited information you have given us, would likely be refactoring this part of the code:

if (isset($_POST['answer'])) {
  $selectedAnswer = $_POST['answer'];
  echo $CorrectAnswer,$selectedAnswer;
  if ($selectedAnswer == $CorrectAnswer)
    echo '+1 pt';
  
}

First, this part of the code has incorrect syntax, and will not be evaluated as an if statement under PHP syntax:

  if ($selectedAnswer == $CorrectAnswer)
    echo '+1 pt';

Please change it to this, so that it complies with the PHP syntax rules:

  if ($selectedAnswer == $CorrectAnswer) {
    echo '+1 pt';
  }

Another issue is that echo $CorrectAnswer,$selectedAnswer; doesn't do anything. echo calls take only one parameter, and need to be wrapped like this: echo(...)

If you intend to echo both those values, you need to join the strings together, like this:

echo ($CorrectAnswer . $selectedAnswer);

As explained in the answer linked above, if you want to add spacing in-between that, you will need to make further changes.

Another problem is here:

while ($row = mysqli_fetch_assoc($res)) { 
  $CorrectAnswer = $row['CorrectAnswer'];
  echo $CorrectAnswer;

Similarly to your if statement, you have not closed this function correctly under PHP, so it won't work under PHP syntax. Here is how you close this correctly:

while ($row = mysqli_fetch_assoc($res)) { 
  $CorrectAnswer = $row['CorrectAnswer'];
  echo $CorrectAnswer;
}

This answer may not help you depending on the structure of your SQL database and what you intend for this program to do. If this does not solve your problem, please provide further clarification. Thanks.

Very nice answer for a first contributer, I'm impressed – Axel Köhler Jan 04 '23 at 13:42 — Axel Köhler, Jan 04 '23 at 13:42

Why is my quiz displaying the wrong 'correct answer'

1 Answers1