Undefined variable: correct in in a simple for loop

Question

it gives me errors in lines 10 and 15, it would be awesome if someone could help me with this :)

<?php

if(isset($_POST["submit"])) {
    for($c = 0; $c < count($questionInf); $c++){
        if(isset($_POST["butn".$c])) {
            array_push($select, $_POST["butn".$c]);
        }
    }
    for($n = 0; $n < 10; $n++){
        if($select[$n] == $correct[$n]){
            $points++;
        }
    }
    echo "Tu dabuji" . $points. "/10 punktus";
    $y = $con->query("SELECT MAX(id) FROM user");
    foreach ($y as $ar) {
        foreach($ar as $yop) {
            $db->query("UPDATE user SET score = ". $points ." WHERE id = ". $yop);
        }
    }
}

?>