$SESSION not working despite numerous tries and search online

Question

I am coding an online quizzer using PHP. Whenever the answerer of the quiz choose the correct answer, the code will automatically +1 to his overall score.

To do that, I used $_SESSION['score']=0; to first set the score to zero and $_SESSION['score']++; whenever the answerer gets the answer correct for each question.

However, I have no idea why the score is not adding up despite the answerers answering the questions correctly.

When the answerer answers the question correctly, the score is still 0 for some reason and I have no idea why. May I know what went wrong? Thank you.

Things I have tried:

1.Changing $_SESSION['score']++; to $_SESSION['score']+1;

2.Changing:

if(!isset($_SESSION['score'])){ $_SESSION['score']=0; }

to just

$_SESSION['score']=0;

3.Changing

if($correct_choice == $selected_choice){ $_SESSION['score']++; }

to just:

if($correct_choice = $selected_choice){ $_SESSION['score']++; }

Below is the code for process.php:

<?php include 'database.php'; ?>
<?php session_start(); ?>

<?php

 if(!isset($_SESSION['score'])){
    $_SESSION['score']=0;

}

if(isset($_POST['submit'])){
    $number=$_POST['number'];
    $selected_choice = $_POST['choice'];
    $next=$number+1;

   /*
    *   Get total questions
    */
    $query="SELECT* FROM questions";
    $results= mysqli_query($con,$query);
    $total=$results->num_rows;

   /*
    *   Get correct choice
    */
    $query = "SELECT* FROM `choices` WHERE question_number = $number AND is_correct=1";
    //Get result
    $results= mysqli_query($con,$query);

    //Get row
    $row=$results->fetch_assoc();

    //Set Correct choices
    $correct_choice=$row['id'];

    //Compare choice made with correct choice
    if($correct_choice == $selected_choice){
        $_SESSION['score']++;
    }


    //Check if last question
    if($number == $total){
        header("Location: final.php");
        exit();
    } else {
        header("Location: question.php?n=".$next);
    }

}

Just tried something:

if($correct_choice == $selected_choice){
        echo "same";
    } else{
        echo "not same";
    }

Even though $correct_choice and $selected_choice are both equals to 1, the code still returns as "not same"?

Answer 1

Make sure that your code does not output anything to the browser before session_start() is called.

you can find more information about $_SESSION superglobal here.

To use cookie-based sessions, session_start() must be called before outputing anything to the browser.

Answer 2

You are opening and closing a lot of PHP tags - unnecessarily. If you have error reporting on, and being displayed on screen, it would likely be saying 'headers already sent'. That, is likely the issue.

Since the process.php file is all php - just open the <?php tag once - and don't even bother to close it at the end - unless you are explicitly outputting something (which is bad practice anyway for a larger program, better to use a small framework, and separate templates).