sample.php

<?php

$score = array();
$negative_score = array();

$answers = ( !empty($_POST['answers']) ) ? $_POST['answers'] : array();


foreach ( $answers as $question_id => $answer ) {
	
	// here you will make a query with the $question_id and compare the database answer with the variable $answer provided by the uder

	$answer_is_true = true; // here you would make a verification that would return either true or false

	// if answer is true
	if ( $answer_is_true ) {
		$score[] = 1; // 1 being the score attributed to this question
	} else {
		$negative_score[] = 1;
	}

}

$score_total = array_sum($score); // sum of the scores
$negative_score_total = array_sum($negative_score); // sum of the scores

// you now have positive score and negative scroe, you just need to subtract the negative score to the total score, like 30 - 20 = 10 score

var_dump($score_total);

?>

<form method="POST">

<p>Question 1</p>
<label>
	<input type="radio" name="answers[1]" value="a" />
	Answer A
</label>

<label>
	<input type="radio" name="answers[1]" value="b" />
	Answer B
</label>

<p>Question 2</p>
<label>
	<input type="radio" name="answers[2]" value="a" />
	Answer A
</label>

<label>
	<input type="radio" name="answers[2]" value="b" />
	Answer B
</label>

<p><button type="submit">Submit</button></p>

</form>