i was try but give up

i have table shipping

id | order_id | supplier_id | shipping_cost
1 37575000001 2 20000
2 37575000001 2 40000
3 37575000001 10 20000
4 37575000001 10 30000

i want to calculate height shipping_cost with same supplier_id
from the table is 40000 and 30000 total_shipping_cost is 70000

i was try with query

<?php
$query = "SELECT shipping_cost FROM shipping where order_id='37575000001' group by supplier_id order by shipping_cost desc";
$result = mysqli_query($conn, $query);
while($row = mysqli_fetch_array($result))
{   
$shipping_cost=$row['shipping_cost'];    
    $total_shipping_cost=$total_shipping_cost+$shipping_cost; 
} 

echo $total_shipping_cost;
?>

but the result is 40000

please help