Sql query store in a variable and use the variable to add something using PHP

Question

how to store a sql query to a variable to add 1 to its current value. I already have a code but it doesn't add 1 to the current value in the select query ['eCorrect'] instead the result will be 2 after submitting the form. And it show this error Object of class mysqli_result could not be converted to int. I have set my 'eCorrect' field to data type INT. I don't know where my error is please help thanks in advance.

<form method="post" action="elQ2.php">
        <p>Question: sample question sample question sample question sample question</p>
        <input type="radio" name="Ctwo" value="wrong">Choice A<br>
        <input type="radio" name="Ctwo" value="wrong">Choice B<br>
        <input type="radio" name="Ctwo" value="correct">Choice C<br>
        <input type="radio" name="Ctwo" value="wrong">Choice D<br>
        <input type="submit" name="submit" value="Submit" class="pull-right">
        </form>
    </div>
</div>

this is my php code

<?php
$correctResult = $db->query("SELECT eCorrect FROM elearn WHERE eID=1");
$wrongResult = $db->query("SELECT eWrong FROM elearn WHERE eID=1");

$addC = $correctResult;
$addW = $wrongResult;
    if(isset($_POST['submit'])) {

if(!empty($_POST['Ctwo'])){
    if($_POST['Ctwo']=="correct")   {

                $eAns = $_POST['Ctwo'];
                $eAns= $addC + 1 ;
                if($update = $db->query("   UPDATE elearn SET eCorrect = '".$eAns."' WHERE eID=1 "))    {
            }else{
                die($db->error);
            }
                echo "Correct Answer";

    }else{
                //Wrong answer
                $eAns = $_POST['Ctwo'];
                $eAns = $addW + 1 ;
                if($update = $db->query("   UPDATE elearn SET eWrong = '".$eAns."' WHERE eID=1 "))  {
            }else{
                die($db->error);
            }   
                echo "Wrong answer";
            }
        } else{
            echo "You must choose an answer";
        }
}
?>

Answer 1

The problem occurs because the $addC and $addW variables are containing resultsets. So actually you are adding +1 to a resultset.

Try to do this instead:

$cRow = $db->query("SELECT eCorrect FROM elearn WHERE eID=1");
$correctResult = $cRow[0];

$wRow = $db->query("SELECT eWrong FROM elearn WHERE eID=1");
$wrongResult = $cRow[0];