Quantity is not being reduced to normal [closed]

I been trying to create a code that reduces an item's quantity by user input. But whenever I tried to enter a number above 10, it doubles its value instead of a normal subtraction. What could be the issue? Here is the php code:

$current_id = $_POST['current_id'];
$quantity = abs(intval($_POST['quantity']));

$query = "SELECT quantity FROM products WHERE pro_id = $current_id";
$result = mysqli_query($con, $query);
$row = mysqli_fetch_array($result);
$current_quantity = $row['quantity'];

$new_quantity = $current_quantity - $quantity;

$query = "UPDATE products SET quantity = $new_quantity WHERE pro_id = $current_id";
$result = mysqli_query($con, $query);

echo $new_quantity;
?>

And here is the ajax script:

$('.quantity').on('input', function() {
  let current_id = $(this).attr('id');
  let quantity = $('#'+current_id).val();

  if ($.trim(quantity).length == 0) {
    return;
  }

  if(quantity.match(/^\d+$/)) {
    $.ajax({
      type: 'POST',
      url: 'php/update_Quantity.php',
      async:false,
      data: {
        current_id: current_id,
        quantity: quantity
      },
      success: function(data) {
        $('#quantity_'+current_id).text(data);
      }
    });
  } else {
    $('#quantity_'+current_id).text("Invalid quantity");
  }
});

I tried changing the data type of the quantity column but it did not do anything.

source https://stackoverflow.com/questions/76157992/quantity-is-not-being-reduced-to-normal