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coding:the_quiz_app_v2

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The Quiz App Version 2

At this point, you should have a basic, working quiz that is pulling questions from a database. If not, take a look at The Quiz App to get started.

This is what your code should look like before we get started, make sure you understand each line (and that it works). Look at the Troubleshooting section below if you run into problems. 

<?php
error_reporting(E_ALL);
ini_set("display_errors", 1);
 
 
require("questions_from_db.php");
 
$size_of_question_list = sizeof($questions);
 
// check if we are in the middle of answering a question (if we are, then
// the random_number will already be set), otherwise, choose a number
 
if(empty($_REQUEST['random_number'])) {
   $random_number = rand(1, $size_of_question_list);  // there is a bug here (we fixed it with the -1)
} else {
   $random_number = $_REQUEST['random_number'];
}
 
 
?>
 
<h1>Quiz</h1>
 
<?php
 
if(!empty($_REQUEST['user_answer'])) {
   $user_answer = $_REQUEST['user_answer'];
   $question_id = $_REQUEST['random_number'];
   echo "<p>You answered '$user_answer' for Question #$question_id</p>";
 
   if($user_answer == $questions[$question_id]['answer']) {
      echo "Correct :)";
   } else {
      echo "Wrong :(";
   }
 
}
 
?>
 
<p><strong>Question: </strong><?= $questions[$random_number]['question']; ?></p>
<form method='post' action='quiz.php'>
<input type='hidden' name='random_number' value='<?= $random_number; ?>' />
<input type='text' name='user_answer' />
<input type='submit' name='answer_button' value='Answer'/>
</form>
 
<p><a href='quiz.php'>Another random question</a></p>

Sessions

You can store information in a session, which can be accessed on each page load. We'll use a session now to track which questions have already been answered, and we can record the name of person taking the quiz for a future high score table.

You can access what is in a session array in the same way you can see what is in a request array: 

print_r($_SESSION);

Let's understand sessions first, separate from the quiz code. Create a new test page and call it testsession.php: 

<?php
session_start();
?>
<html>
<body>
<?php
if(!empty($_REQUEST)) {
        print_r($_REQUEST);
}
 
if(!empty($_REQUEST['visitor_name'])) {
        $_SESSION['visitor_name'] = $_REQUEST['visitor_name'];
}
 
if(!empty($_SESSION['visitor_name'])) {
        echo "<p>Welcome ".htmlentities($_SESSION['visitor_name'])."</p>";
}
 
 
?>
<form method='post' action=''>
<input type='text' name='visitor_fullname' />
<input type='submit' name='username_button' value='Login' />
</form>
<?php
 
?>

The above code has an error in it. See if you can spot where. I'll talk people through it.

I'll add to this page as we go through on the night.

Some functions we'll need:

phpinfo();

Troubleshooting

I just get a blank white screen or HTTP ERROR 500

Add some error reporting to the very top of your code: 

error_reporting(E_ALL);
ini_set("display_errors", 1);

Remember to also add to any other files you might be including [or require()'ing]

I'm getting an ''Uncaught PDOException: SQLSTATE[HY000] [1045] Access denied'' error

Make sure you are using the correct credentials in questions_from_db.php. If you are unsure, you can set them again by connecting to your mysql server on the terminal: 

sudo mysql -u root

Then, inside the mysql client, create a user called ‘coding_username’, with the password ‘cheese’ and give it access to the newly created ‘coding’ database: 

grant all on coding.* to coding_username@localhost identified by 'cheese';
quit

Notice we use 'coding_username' - make sure that is what is in your questions_from_db.php file.

Uncaught Error: Call to a member function fetchAll() on boolean

Make sure you have questions in your quiz_questions table (login with Adminer to check)

Quiz App with Session Management

<?php
session_start();
error_reporting(E_ALL);
ini_set("display_errors", 1);
?>
<h1>Quiz</h1>
<?php
 
if(!empty($_REQUEST['logout'])) {
        session_destroy();
        $_SESSION = null;
}
 
if(!empty($_REQUEST['player_name'])) {
        $_SESSION['player_name'] = $_REQUEST['player_name'];
}
 
if(empty($_SESSION['player_name'])) {
        ?>
        <p>Welcome to the quiz, enter a name to begin:</p>
        <form method='post' action=''>
        <input type='text' name='player_name' placeholder='Your name' />
        <input type='submit' name='login_button' value='Start' />
        </form>
        <?php
        exit();
}
 
$player_name = $_SESSION['player_name'];
 
require("questions_from_db.php");
$number_of_questions = sizeof($questions);
 
if(!empty($_REQUEST['user_answer'])) {
   $user_answer = $_REQUEST['user_answer'];
   $question_id = $_REQUEST['random_number'];
   echo "<p>You answered '$user_answer' for Question #$question_id</p>";
 
   if($user_answer == $questions[$question_id]['answer']) {
        echo "Correct :)";
        $_SESSION[$player_name]['correct'][$question_id] = $question_id;
   } else {
        echo "Wrong :(";
        $_SESSION[$player_name]['wrong'][$question_id] = $question_id;
   }
 
}
 
 
$correct_answers = $wrong_answers = 0;
if(!empty($_SESSION[$player_name])) {
        if(!empty($_SESSION[$player_name]['correct']))
        $correct_answers = sizeof($_SESSION[$player_name]['correct']);
        if(!empty($_SESSION[$player_name]['wrong']))
        $wrong_answers = sizeof($_SESSION[$player_name]['wrong']);
        if(!empty($_SESSION[$player_name]['correct'])) {
                foreach($_SESSION[$player_name]['correct'] as $question_id) {
                        unset($questions[$question_id]);
                }
        }
        if(!empty($_SESSION[$player_name]['wrong'])) {
                foreach($_SESSION[$player_name]['wrong'] as $question_id) {
                        unset($questions[$question_id]);
                }
 
        }
}
 
$total_answered = $correct_answers + $wrong_answers;
 
echo "<p>You've answered $total_answered questions.  $correct_answers right, $wrong_answers wrong.</p>";
 
 
$available_questions = $number_of_questions - $total_answered;
?>
 
<h2>Welcome <?= htmlentities($_SESSION['player_name']); ?></h2>
<a href='quiz.php?logout=1'>Logout</a>
<?php
 
if($available_questions > 0) {
        $random_question_id = array_rand($questions);
?>
 
<p><strong>Question: </strong><?= $questions[$random_question_id]['question']; ?></p>
<form method='post' action='quiz.php'>
<input type='hidden' name='random_number' value='<?= $random_question_id; ?>' />
<input type='text' name='user_answer' />
<input type='submit' name='answer_button' value='Answer'/>
</form>
 
<p><a href='quiz.php'>Another random question</a></p>
<?php
} else {
?>
        <p>You've answered all the questions!  Your score was <?=$correct_answers;?> out of <?= $number_of_questions; ?>!</p>
<?php
        if(empty($_SESSION[$player_name]['score_saved'])) {
                $sql = "insert into high_scores set name=?, correct=?, wrong=?, created_on=now()";
                $insert_stmt = $db_connection->prepare($sql);
                if($insert_stmt->execute([$player_name, $correct_answers, $wrong_answers])) {
                        echo "Highscore saved!";
                } else {
                        echo "Error saving highscore";
                        echo print_r($insert_stmt->errorInfo());
                }
        } else {
                echo "High score already saved.";
        }
 
}
?>
coding/the_quiz_app_v2.txt · Last modified: 2023/06/26 03:11 by admin

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