My html cart system only out total price until 999.99 if lets say the total price is 1890.00 it only prints 189.00 [closed]

Here is the code

 
            
            <td>RM<?php echo number_format($fetch_cart['price']); ?>/-</td>
            <td>
               <form action="" method="post">
                  <input type="hidden" name="update_quantity_id"  value="<?php echo $fetch_cart['id']; ?>" >
                  <div class="num">
                  <input type="number" name="update_quantity" min="1"  value="<?php echo $fetch_cart['quantity']; ?>" >
                  </div>
                  <input type="submit" value="update" name="update_update_btn">
               </form>   
            </td>
            <td>RM<?php echo $sub_total = number_format($fetch_cart['price'] * $fetch_cart['quantity'],2); ?>/-</td>
            <td><a href="cart.php?remove=<?php echo $fetch_cart['id']; ?>" onclick="return confirm('remove item from cart?')" class="delete-btn"> <i class="fas fa-trash"></i> remove</a></td>
         </tr>
         <?php
           $grand_total .= $sub_total;  
            };
         };
         ?>
        

      </tbody>

i tried formating but its not working but there is a error showing saying non-numeric value at

  <?php
           $grand_total .= $sub_total;  
            };

is there a solution fr this problem ive searched google many time but not working