PHP select and fetch - php

Question

This question is about a quiz and I wish to prevent the user from submitting the same question and receiving points several times for a single correct answer.
I have a db where I store the user's correct questions and a select statement,
but it is only inserting and not reading the argument for a user that is already in that db.
The score is added corectly, bubt the only issue it's not validating user_corect_question db, the code just keeps adding new lines to the db and points to the user.
tnx!
//if corect answer
if($corect_choise == $selected_choise){
//check if user answered corect and recieved points for this question before
$query = "SELECT corect FROM user_corect_question WHERE location_id=$location_id and userid=$userid and corect=1";
//get result
$result = $mysqli->query($query) or die ($mysqli->error.__LINE__);
//get row
$row = $result->fetch_assoc();
// if did not recive points for this question insert to user corect questions db
if($row != 0){
//get user score
$query="SELECT score FROM `members` WHERE userid = $userid";
//get result
$result = $mysqli->query($query) or die ($mysqli->error.__LINE__);
$row = mysqli_fetch_array($result);
//echo $row['score'];
//points for corect answer
$score = 1;
//user score+ new points
$_SESSION['score'] = $score + $row['score'];
//save new score
$new_score= $_SESSION['score'];
$query = "UPDATE `members` SET score='$new_score' WHERE userid=$userid ";
//get result
$result = $mysqli->query($query) or die ($mysqli->error.__LINE__);
//redirect to score
header("Location: ../final2.php") ;
}
else{
$corect = 1;
$query = "INSERT INTO user_corect_question (location_id,userid,corect) VALUES ('$location_id','$userid','$corect')";
// save to db
$DB = new Database();
$DB->save($query);
//get user score
$query="SELECT score FROM `members` WHERE userid = $userid";
//get result
$result = $mysqli->query($query) or die ($mysqli->error.__LINE__);
$row = mysqli_fetch_array($result);
//echo $row['score'];
//points for corect answer
$score = 25;
//user score+ new points
$_SESSION['score'] = $score + $row['score'];
//save new score
$new_score= $_SESSION['score'];
$query = "UPDATE `members` SET score='$new_score' WHERE userid=$userid ";
//get result
$result = $mysqli->query($query) or die ($mysqli->error.__LINE__);
//redirect to score
header("Location: ../final.php") ;
}
}
else{
header ("Location: ../try_again.php"."Try again");
}

Answer 1

If the user already has a record there, then the program lands in the if branch.
//points for corect answer
$score = 1;
//user score+ new points
$_SESSION['score'] = $score + $row['score'];
//save new score
$new_score= $_SESSION['score'];
$query = "UPDATE `members` SET score='$new_score' WHERE userid=$userid ";
This adds some points to the user. You don't need this in the if branch.