PDO func insert and multiplilcation

im trying to make function that take every row from column inv by user id multiply it by 0,015 and then insert this value to zhod with same user id.

i have this but im lost already. if someone can help or simplify it ill be glad.

public function updateZhod($id) {
   $sql = "UPDATE users SET zhod = inv * 0.015 WHERE id = :id AND verified = 1";
    $stmt = $this->conn->prepare($sql);
    $stmt->bindParam(':id', $id);
    $stmt->execute();
}

if (isset($_POST['action']) && $_POST['action'] == 'fetchAllUsersInv') {
    $output = '';
    $data = $admin->fetchAllUsersInv(0);
    if ($data) {
        $output .= '<table class="table table-striped table-bordered text-center">
                        <thead>
                            <tr>
                                <th>ID</th>
                                <th>Inv</th>
                <th>Zhod</th>
                            </tr>
                        </thead>
                        <tbody>';

        foreach ($data as $row) {
            $zhodValue = $row['inv'] * 0.015;

            $output .= '<tr>
                            <td>' . $row['id'] . '</td>
                            <td>' . $row['inv'] . '</td>
                            <td>' . $zhodValue . '</td>
                        </tr>';
        }

        $output .= '</tbody>
                    </table>';

        echo $output;
    } else {
        echo '<h3 class="text-center text-secondary">:( No inv</h3>';
    }
}


if (isset($_POST['action']) && $_POST['action'] == 'updateZhod') {
    $admin->updateZhod();

    echo 'Zhod values updated successfully!';
}

<script>
    $(document).ready(function() {
        $("#zhodLed").click(function() {
            $.ajax({
                url: 'assets/php/admin-action.php',
                type: 'POST',
                data: {
                    action: 'updateZhod'
                },
                dataType: 'json',
                success: function(response) {
                    if (response.success) {
                        $("#invValue").text(response.newValue.toFixed(2) + " ...");
                    } else {
                        alert("Error: Failed to update zhod value.");
                    }
                },
                error: function(jqXHR, textStatus, errorThrown) {
                    console.error("AJAX Error:", textStatus, errorThrown);
                    alert("Error: Unable to make the AJAX request.");
                }
            });
        });
    });
</script>

this should be simple func that take one value from inv multiply it by 0,015 and insert it to zhod but its probably behind my skills