Errors in prepared statement

I get the following error

Notice: Undefined variable: prepared_stmt in “// Fetch the result”

My code is:

    // The prepared statement
    $sql = $pdo->query('SELECT * FROM table1 WHERE answer LIKE :answer');
    while ($row = $sql->fetch())
    {
        echo $row['name'] . "n";
    }

    // Prepare, bind, and execute the query
    $prepared_stmt->bind_param(':answer', $searchString);
    $prepared_stmt->execute();

    // Fetch the result
    $result = $prepared_stmt->get_result();

    if ($result->num_rows === 0) {
        // No match found
        echo "No match found";
        // Kill the script
        exit();

    } else {
        // Process the result(s)
        while ($row = $result->fetch_assoc()) {
            echo "<b>Qn Number</b>: ". $row['qnumber'] . "<br />";
            echo "<b>Question</b>: ". $row['questionr'] . "<br />";

        } // end of while loop
    } // end of if($result->num_rows)

Could someone help me out?