Comparing values in PHP and MYSQL

PHP
1

I am have been attempting to compare values selected from a MYSQL to a PHP array. My problem is that I can print out the array to see the values but i am not sure how to compare the MYSQL values to what is in the array. As in the code i have provided i have attempted to use an if else statement but does not work how i expected to as it does not compare the answer but still echos out the use response is incorrect . I would really appreciate it someone could look over my code and give me some guidance as to where i am going wrong.

I have included the two php pages i am currently working with

Answer Question Page

		   
	<?php
     require_once ('mysqli_connect.php');
	 
$q = "SELECT * FROM multiplechoice_db ORDER BY RAND() LIMIT 2";		
$result = @mysqli_query ($dbcon, $q); // Run the query
if ($result) { // If it ran OK, display the records
?>
<form action="answerquiz.php" method="GET">
<table>
<tr>
<td><b> For Each Question There will Only Be One Possible Answer</b> </td>
<br>
</tr>
<?php
// Fetch and print all the records
while ($row = mysqli_fetch_array($result, MYSQLI_ASSOC)) {
$question = $row['question'];
$question_id = $row['question_id'];
$option_1 = $row['option_1'];
$option_2 = $row['option_2'];
$option_3 = $row['option_3'];
$option_4 = $row['option_4'];
?>
<tr>
<tr>
<td>
<br>
<br>

<ol><li><?php echo $question;?></li></ol>

1.<input type="radio"   name = "question_id[<?php echo $question_id;?>]" value= "1" /><?php echo $option_1;?> 
<br>
2.<input type="radio"   name = "question_id[<?php echo $question_id;?>]" value= "2" /><?php echo $option_2;?>  
<br>
3.<input type="radio"   name = "question_id[<?php echo $question_id;?>]" value= "3" /><?php echo $option_3;?> 
<br>
4.<input type="radio"   name = "question_id[<?php echo $question_id;?>]" value= "4" /><?php echo $option_4;?> 
<br>
<td>
<td>
<td>
<td>
</td>
</tr>
<?php
	}

?>


	 </table>
	<br>
	<input type ="submit" value="Submit Quiz">
	
	</form>

<?php	
}
	?>

answer_quiz page

 
require ('mysqli_connect.php');
if(isset($_REQUEST['question_id']) ){
    $arr_question_id = $_REQUEST['question_id'];
    //$question = '3';	
   // print_r($arr_question_id);

   $learner_response= "SELECT question_id, answer FROM multiplechoice_db WHERE question_id = 'question_id' AND answer = 'answer'";
   $result=@mysqli_query($dbcon, $learner_response);
    while ($row = mysqli_fetch_array($result, MYSQLI_ASSOC)) {
   $question_id = $row['question_id'];
   $answer = $row['answer'];
   }
   $correct_answer=0;
   $incorrect_answer=0;
 
 //if ($result == FALSE)
//{
 //die(mysqli_error($dbcon));
 //}
 foreach($arr_question_id as $question_id=>$option_value){
 print " Question id: " .$question_id.    
       "Learner Response: ". $option_value.  "\
";
 }
 
      //while ($row = mysqli_fetch_array($result)) {
	  foreach($arr_question_id as $question_id=>$option_value){
       if($row['answer'] == $option_value){
	         echo ' You have answered the Question Correct';
             $correct_answer++;
           }else{
              echo ' You have answered the Question Incorrect';
              $incorrect_answer++;
          }
		   
		 
  "Numbers of correct answer : ". $correct_answer."<br>";
  "Numbers of correct answer  : ". $incorrect_answer."<br>";
}
}
2

The following line in your script doesn’t seem to make any sense:


$learner_response= "SELECT question_id, answer FROM multiplechoice_db WHERE question_id = 'question_id' AND answer = 'answer'";

Surely the question_id variable from the HTTP GET data should be used in the query, along with the answer provided? Hard-coding the values seems pretty useless to me.

Here’s a print_r of the HTTP data your answer quiz page should be receiving:


Array
(
	[question_id] => Array
	(
		[1] => 1
		[2] => 2
	)
	[submit] => Submit Quiz
)

(With the values in the question_id array subject to change according to what your quiz question query returns.)

So we can see that the keys of the question_id array are the keys of the random questions from the database, and they are pointing the user-submitted values. So let’s loop through the question_id array:


if(isset($_POST['submit'])) {
	foreach($_POST['question_id'] as $qID => $qVal) {
		// body
	}
}

(Note that I’ve changed your HTTP method to POST, since I believe it to be more suitable the GET in this instance.)

We now have a method of checking each question and its respective submitted answer, so let’s update the body of our foreach loop to query against the database:


if(isset($_POST['submit'])) {
	foreach($_POST['question_id'] as $qID => $qVal) {
		$qID = (int) $qID;
		$qVal = (int) $qVal;

		$learnerResponse= "SELECT COUNT(*) AS rightAnswer FROM multiplechoice_db WHERE question_id = {$qID} AND answer = {$qVal}";
		$result = mysqli_query($dbcon, $learnerResponse);
		$row = mysqli_fetch_array($result, MYSQLI_ASSOC);

		if($row['rightAnswer']) {
			// correct answer for question with ID of $qID
		}else{
			// wrong answer
		}
	}
}

Notice that I’ve casted the question ID and answer to integers (since that’s their type according to your quiz form) for security reasons. The query now gets a COUNT of the number of rows found for each submitted question and answer. If a row is found (i.e. a question and their respect answer matches), then a count of 1 will be returned, otherwise 0 will be returned.

3

Instead of using the LIMIT and ORDER BY clauses, consider the using array_rand()

4

Thanks for the help, you explanation was really helpful . I have one more question in relation to the if else statement I will be using. As in the code below if the answer the user gives is correct I want a statement to be printed out on the webpage telling the user they have got the question correct or if incorrect a statement they have got the question incorrect. I have ran the code the code you provided and added in the echo statements i wanted but I keep getting a blank page. Once again I am not sure what I am doing wrong as i have used php if else statements before without issue. Any guidance would be much appreciated.

 if($row['rightAnswer']){
	         echo ' You have answered the Question Incorrect';
            }else{
             echo ' You have answered the Question Incorrect';
           
          }
5

Could you execute the following instead of the above script (it just includes a var_dump() for debugging information and an ini setting to ensure errors are displayed) to help see what your problem is:


ini_set('display_errors', '1');
error_reporting(-1);
var_dump($_POST);
if(isset($_POST['submit'])) {
    foreach($_POST['question_id'] as $qID => $qVal) { 
        $qID = (int) $qID; 
        $qVal = (int) $qVal; 

        $learnerResponse= "SELECT COUNT(*) AS rightAnswer FROM multiplechoice_db WHERE question_id = {$qID} AND answer = {$qVal}"; 
        $result = mysqli_query($dbcon, $learnerResponse); 
        $row = mysqli_fetch_array($result, MYSQLI_ASSOC); 

        if($row['rightAnswer']) { 
            // correct answer for question with ID of $qID 
        }else{ 
            // wrong answer 
        } 
    } 
}
6

Once i run the above my output is:

array (size=1)
‘question_id’ =>
array (size=2)
11 => string ‘2’ (length=1)
2 => string ‘1’ (length=1)

I checked the answers to the two questions in the array against the matching id and answer in the database and they were both correct. However if I run the code with two answers I know are incorrect I get the same output. I have limited knowledge of php and arrays but I am starting to think that there might be an issue with the data actually reaching the if statement ?

7

The problem is that the body of the IF statement (checking to see if $_POST[‘submit’] is submitted) is not executing. This is because you haven’t named your submit button:


<input type="submit" name="submit" value="Submit Quiz">

Keep the script in my original post, but replace your submit button line with the above and things should work as expected.

8

It works !!! Thank you so much for all your help !!!